The contraceptive vaginal sponge was developed as an alternative to the contraceptive diaphragm. Unlike the diaphragm, the sponge can be used for more than one coital act within 24 h without the insertion of additional spermicide, and it does not require fitting or a prescription from a physician. We conducted a systematic review of randomized controlled trials that compared the vaginal contraceptive sponge with the diaphragm used with a spermicide in order to evaluate the efficacy and continuation rates of the two devices. The sponge was statistically significantly less effective in preventing overall pregnancy than was the diaphragm in the two trials that met our inclusion criteria. The 12-month cumulative life table termination rates per 100 women for overall pregnancy were 17.4 for the sponge versus 12.8 for the diaphragm in the larger US trial, and 24.5 for the sponge and 10.9 for the diaphragm in the UK trial. Similarly, discontinuation rates at 12 months were higher with the sponge than with the diaphragm [odds ratio 1.3; 95% confidence interval (CI) 1.1-1.6]. Allergic-type reactions were more common with the sponge in both trials, although the frequency of discontinuation for discomfort differed in the two trials. Other randomized controlled trials will be needed to resolve the role of spermicides in preventing sexually transmitted infections or in causing adverse effects.