The development of a male contraceptive pill may have been advanced by the discovery of a genetic defect that can cause infertility in men.
Research on mice, reported in the American Journal of Human Genetics, shows that the gene Catsper1 induces the energetic motion of sperm needed to penetrate the egg during fertilisation.
Dr Michael Hildebrand at the University of Iowa says: "It suggests that the defect in sperm hyperactivity seen in mice without Catsper1 will also occur in humans.
"Identification of targets that are involved in the fertility process and are specific for sperm ... provide new targets for a pharmacological male contraceptive."
Teams of scientists worldwide are already investigating possible avenues of research. One that might involve Catsper1 is immunocontraception, which relies on antibodies to block a protein's function.
Surveys conducted by the Medical Research Council suggest that men would be willing to use a contraceptive pill. The female version was developed more than 40 years ago, and is the most widely used form of birth control.