Rabbit antisera elicited by injection of human oviductal fluid (HOF) and rendered specific by absorption with human kidney and human serum revealed the presence of two possibly HOF-specific antigen(s). One antigen was detected by immunodiffusion in 14 of the 14 fluids tested with one of these antisera. HOF-specific antigen was shown to be a beta-globulin by immunoelectrophoresis. A second antigen was seen in two samples. That autoantibodies might exist directed against HOF-specific antigen in the donor's serum was suggested by immunodiffusion experiments in which 4 of the 13 sera tested gave lines of precipitation when reacted against the corresponding oviductal fluid. In one instance, this line was the same as one of the two lines seen in tests using rabbit antiserum.