Gardnerella vaginalis was isolated from 22 (38%) of 58 semen samples obtained from men attending an infertility clinic. Counts ranged from 1P2 x 103 to >10' colonly forming units (cfu)/ml. There was no association between the isolation of G vaginalis and the sperm count. Twenty (34 4%) samples contained non-sporing anaerobes and nine (15 50o) both anaerobes and G vaginalis. The infective dose of G vaginalis is not known, but semen could act as a medium for its sexual transmission.