Markush Claims – What Are They, When Should I Use One, and How Do I Use One?

While many diverse areas of patent law are important to practicing competently, it is the claims which share center stage.  It is the claims which define and carve out the scope of the invention.  During the patent prosecution phase, it is the claims which are fought over.  And again during patent infringement suits, it is the claims which play center stage and must be interpreted to determine whether there is infringement or not, i.e. the claims get constructed via an infamous Markman Hearing.  There are many very technical treatises addressing all the nuisances to claim drafting and there are many different types and styles of claims.  Here, we will briefly explore one such type of claim, the “Markush Claim.”

A Markush claim is a type of claim most often used to conserve writing additional claims, which can be financially important because the standard filing fees in a non-provisional patent application only include twenty total claims, three of which may be independent.  The Markush claim allows a patent drafter to select a particular element of the invention wherein that element may be selected from a group of elements all sharing some common characteristic.  Generally, without using a Markush claim, the drafter would instead have to write a series of dependent claims claiming use of each of the elements selected from the group.  Whereas, if the Markush claim is used instead, what may have been a multitude of dependent claims can now be condensed into a single claim.

Consider the following Markush claim:

“an alkali metal selected from the group consisting of lithium, sodium, and potassium”

In this example, what this Markush claim does in one claim, would otherwise take three claims, which quickly eats into the allotted amount of claims.  Also note that while the group of “alkali metals” is a well-defined group with six metal comprising the full family, the sub-group of alkali metals listed in the example have no proper nomenclature to identify such a sub-group and thus the Markush claim is also used not just to conserve claim number, but out of necessity, to create a generic name for some sub-group that may otherwise have no well-defined name.

One also might note that using a Markush claim is an exception to the general prohibition against alternative claiming, in that a Markush claim is certainly a form of alternative claiming.  Historically, the case that initially sanctioned use of the Markush claim involved this claim: “a material selected from the group consisting of aniline and halogen substitutes of aniline,” i.e. this was an example where the sub-group identified in the claim had no name that could readily identify such a sub-group, and so use of this claim was out of necessity. In reviewing this claim, the then Commissioner recognized such a necessity and thus created the Markush doctrine we all use today.  Ex parte Markush, 1925 C.D. 126 (Comm’ Pat.1925).

Note, while the above example and the original historic Markush claim involved selecting a species from a group of chemicals, use of Markush claiming may be done in any of the recognized statutory classes under section 101, i.e. the Markush form of alternative claiming may be done with processes, machines, articles of manufacture, and of course compositions of matter.  However, with some mechanical inventions and process inventions (method claims), in many situations where a Markush claim could be used, a “means for” or “step for” claim could just as well be utilized.  For example, consider a table as an invention, where a claim is claiming how legs may be attached to the table.  In Markush claim language, such a claim might read, “…wherein a fastener selected from the group consisting of nails, screws, and bolts.”  Or instead this claim could be addressed with a means for claim of, “a means for fastening…”  A means for clause works here because there exists a word to generically describe the intended function here, i.e. “fastening.”  Where no such generic word exists, the Markush claim makes sense.  Means for and step for claims are beyond the scope of this article, and are governed by 35 U.S.C. section 112(f) (former known as “paragraph 6”) and the case law interpreting that provision.

So how do you draft a Markush claim?  A Markush claim generally has two accepted forms of implementing:

 “an alkali metal selected from the group consisting of lithium, sodium, and potassium”


“an alkali metal is lithium, sodium, or potassium”

Note in the first form, to use a proper Markush claim one must use the transition word of “consisting of” along with the conjunctive “and.”  This simply means that group is a closed group which is important in avoiding an indefiniteness rejection.  The second form is also an accepted form of claiming in Markush style, wherein “or” is used instead of “and” and “consisting of” is omitted alotogether.  Do not mix and match the first form with the second form, i.e. the second form should not use “and.”

Lastly, we discuss a limitation in using Markush claims.  The elements listed in the group from which a selection is being made must share a characteristic or property.  For example, the elements in the group should “belong to a recognized physical or chemical class or an art-recognized class.”  MPEP 2173.05(h).  Further,

it is sufficient if the members of the group are disclosed in the specification to possess at least one property in common which is mainly responsible for their function in the claimed relationship, and it is clear from their very function in the claimed relationship, and it is clear from their very nature or from the prior art that all of them possess this property.  Id.

Thus, out of caution, it is a best practice to explicitly state what the shared property for a group is in the patent specification.  And if the level of abstraction for the shared characteristic is too broad, a patent examiner may very well reject the claim resulting in a need to amend the claim using several ordinary dependent claims.  Note there are other issues to consider with Markush claims, such as double-patenting and restriction requirements, but we will save those issues for another article.  In general, see MPEP 2173.05(h) for further information on Markush claiming.

Eric Kelly
Orange County Patent Attorneys