There is no official Greek life at the Claremont Colleges. Because of the small campus sizes and low number of students, Greek life would only promote unnecessary segregation among students. Students at Pitzer can attend parties at any of the other campuses (except for the few parties that are school-exclusive), so there is really no need for a Greek life to enhance the social aspects of the school.
There is some "underground" Greek life, but these one or two organizations in no way define the social scene. Students at Pitzer do not mind that there is no Greek life; actually, a great number of students prefer that there is no Greek life, and some apply to Pitzer specifically for that reason.