An aetiological role for non-specific genital tract infection (GTI) in male infertility has long been postulated and has led to routine bacteriologic culture of semen in some laboratories. To assess the value of examination of various semen characteristics and conventional culture of semen as diagnostic criteria for GTI, frequencies of bacterial isolation and relationships with leukocytospermia and other abnormalities of semen were determined in 806 samples from 459 men seen over a 2 year period. Combinations of features suggestive of GTI were present in 19.6%. High leucocyte counts were found in 13.5% of specimens and evidence of possible accessory sex organ dysfunction in 57.7%. Significant numbers of bacteria were isolated from 19.5% of samples. Of the few pathogens cultured (46 specimens), 53% were Staphylococcus aureus, a possible contaminant. Furthermore, only one specimen had more than 10(6) pathogenic bacteria per ml, also Staph. aureus. There was a lack of correlation between the presence of bacteriospermia, leukocytospermia and semen changes possibly attributable to accessory sex organ dysfunction, shedding doubt on their relevance to identification of GTI. This was the case even in repeatedly culture-positive specimens. Conventional bacteriological examination of semen specimens is not merited as a routine procedure.