For the past 25 years commentators have struggled with operative provisions of the tax law that, directly or indirectly, focus on the distinction between types of members of unincorporated business entities.  Between 1979 and 2001 the law of unincorporated business entities evolved dramatically, but there has been little progress in identifying the distinctions between general partners and limited partners for federal income tax purposes.  There also has been little progress in characterizing as general partners or limited partners the members of limited liability entities (LLEs) (other than state law limited partnerships) who are treated as "partners" for tax purposes.  In large part, this lack of progress may be directly attributable to actions of Congress, as discussed in this article.  At the same time, other tax laws and business laws have evolved in a way that places greater stress and importance on these distinctions. One thing that has not changed over the last 25 years: tax practitioners still need to know how to apply operative tax provisions to LLEs and their owners.