The clastogenicity of a potential male contraceptive, gossypol, was examined in cultured Chinese hamster cells with and without the presence of a metabolic activation system (rat liver S9 mix). Gossypol at concentrations of 1, 5, and 10 micrograms/ml did not induce chromosome breakage either in the presence or absence of the S9 mix. The ability of this compound to induce chromosome breakage and polyploidy was further examined in human lymphocyte cultures. Neither increased frequencies of chromosome breakage nor polyploidy was found in lymphocyte cultures from two healthy donors. The present study indicates that gossypol does not cause genetic damage at the chromosomal level. This is consistent with previously reported findings that it does not produce mutations in the Ames test. Gossypol has been under clinical trial in China for years and shown to be effective in 99.9% of over 10,000 men tested with no or mild side effects. If this compound can be further proven to be "safe" and approved for world-wide use as a male contraceptive, it would be for the benefit of all mankind.