From 1981-1988, 3433 women were fitted with a cavity-rim cervical cap in a Food and Drug Administration-approved study. The estimated first-year pregnancy risk was 11.3% (95% confidence limits 10.0-12.8), with risks of 8.3 and 3.8% for user and method failures, respectively. Women who were younger, less educated, and more sexually active, and who intended to have children in the future, had higher pregnancy risks. "Near-perfect" users, ie, individuals who wore the cap for a maximum of 72 hours, used spermicide 100% of the time, and did not report unprotected sexual intercourse, had half the first-year pregnancy risk of others (6.1 versus 11.9%). There were no serious medical or gynecologic complications associated with cap use, although over 20% of users reported problems with cap dislodgment during or after intercourse, cap malodor, or partner discomfort.