This review provides an updated analysis of the first-year probabilities of contraceptive failure for all methods available in the United States. It compares pregnancy rates during typical use (including both incorrect and inconsistent use) and perfect use (correct and consistent use). The difference between these two probabilities highlights the consequences of imperfect use, which depends on how forgiving a method is of imperfections and how difficult it is to use perfectly. The estimates are based on new research on contraceptive failure during both typical and perfect use, derived from surveys and clinical trials. The review also discusses the effectiveness of various methods, such as spermicides, withdrawal, fertility awareness-based methods, diaphragms, male condoms, oral contraceptive pills, and Depo-Provera, among others. It emphasizes the importance of understanding both typical and perfect use to make informed decisions about contraceptive methods.This review provides an updated analysis of the first-year probabilities of contraceptive failure for all methods available in the United States. It compares pregnancy rates during typical use (including both incorrect and inconsistent use) and perfect use (correct and consistent use). The difference between these two probabilities highlights the consequences of imperfect use, which depends on how forgiving a method is of imperfections and how difficult it is to use perfectly. The estimates are based on new research on contraceptive failure during both typical and perfect use, derived from surveys and clinical trials. The review also discusses the effectiveness of various methods, such as spermicides, withdrawal, fertility awareness-based methods, diaphragms, male condoms, oral contraceptive pills, and Depo-Provera, among others. It emphasizes the importance of understanding both typical and perfect use to make informed decisions about contraceptive methods.