There is a growing awareness that, in some situations, environmental hazards to male reproduction must be studied directly in exposed men as well as in animal models. The tests which are available for human reproductive surveillance are those which have been applied clinically in assessing male infertility. There has been significant improvement of these clinical tests during the past ten years and several new tests have been recently developed. The application of this new technology for risk surveillance of reproductive hazards offers the possibility of greater accuracy in detecting early signs of human male reproductive toxicity. However, effective use of these tests for environmental assessment will also require an appreciation of their biological basis and clinical limitations.