Cluster analysis of hybridizing Lepomis gibbosus (pumpkinseedsl and L. macrochirus (bluegills) collected in Lake Opinicon, Ontario, using data on 20 morphological characters in 108 specimens, revealed three groups, the two parental species and a group of hybrids, all of which were clearly separated by discriminant analysis. Discriminant functions based on the red opercular flap, the pharyngeal dentition, and body depth, correctly assigned all specimens to the appropriate group. Discriminant functions are also reported for external characters only, but the assignment to groups is not perfect. A sample of L. gibbosus, taken from a locality in which other Lepomisspecies were not present, was found to be very similar to the Lake Opinicon sample of this species. The hybrids of Lake Opinicon do not appear to backcross frequently with the parental species, possibly because of nonintermediacy in reproductive behaviour.