The structure of the male genitalia of Anopheles albimanus Wied. is affected by larval rearing temperature. Morphometric analyses of 50 specimens revealed significant variation of 5 genitalic characters. The gonocoxa, dorsal claspette lobes, and aedeagus were longer for males reared at 22 degrees C. The parabasal seta was longer and the aedeagus was wider for males reared at 30 degrees C. Extra parabasal setae and lateral projections of the aedeagus were seen on some specimens.