The modern management of male subfertility is based on recognition and correction of the underlying defect. Treatment starts nonspecifically with improvement in the general environment of spermatogenesis and any surgical abnormalities are dealt with. If supplementary endocrine treatment is necessary it is given rationally after estimation of pituitary and testicular hormone levels. The presence or absence of antisperm antibodies is established and their effect on sperm behaviour is observed before and during treatment. Progress in understanding the complex processes involved in human reproduction requires careful observation of accurately defined facts. Much research remains to be done.