The long-term objective of this proposal is to develop a safe non- hormonal oral male contraceptive that has post-testicular mode of action. The proposal is based on the observation that ketoconazole, a safe oral human fungicide causes, causes ejaculation of spermatozoa which are immobilized. Administration of ketoconazole to rats renders them infertile. Based on the structure of ketoconazole (1), which is a N- substituted 1 (H)-imidazole, it is proposed to synthesize a series of analogous C-substituted imidazoles (2) for evaluation.