Dr. Trussell's primary research focus over the past decade has been the analysis of contraceptive efficacy. In more than a dozen papers, he has changed the way that clinical trials of contraceptives are designed, executed, and analyzed so that separate methodologically sound estimates of the risks of pregnancy during perfect use and during typical use of contraceptive methods can be derived. His particular substantive contribution has been a string of empirical analyses demonstrating the efficacy of the sponge, cervical cap, diaphragm, female condom, and ovulation method of periodic abstinence. His protocol for male condom slippage and breakage studies is now universally adopted as the standard. His 1987 meta-analysis of the literature on contraceptive failure, regularly updated in Contraceptive Technology, considered the bible of the field, has resulted in a summary table of contraceptive efficacy that is mandated by the Food and Drug Administration to appear on every contraceptive drug and device sold in the United States.