We have noted in a group of oligospermic patients with normal FSH levels and normal sized testes that there can be a significant drop in the LH levels estimated by IRMA, compared with a control group of fertile men. On the other hand, there is no correlation between IRMA and RIA levels of LH in oligospermic men when there is such a correlation in the control group. As oligospermia is usually testicular in origin preliminary results suggest that there may be a disturbance of gonadotrophin secretion in one type of oligospermia and we intend to continue this preliminary study.