Hugh Pickens writes "The BBC reports that recent tests in China indicate a monthly injection of testosterone, which works by temporarily blocking sperm production, could be as effective at preventing pregnancies as the female pill or condoms. In trials in China only one man in 100 fathered a child while on the injections, and six months after stopping the injections the mens' sperm counts returned to normal. The lead researcher said that if further tests proved successful, the treatment could become widely available in five years' time. Previous attempts to develop an effective and convenient male contraceptive have encountered problems over reliability and side effects, such as mood swings and a lowered sex drive. However, despite the injection having no serious side effects, almost a third of the 1,045 men in the two-and-a-half year study did not complete the trials; no reason was given for this."