CONTEXT: Though contraceptive failure and induced abortion in China have both attracted research attention, the somewhat broader topic of unintended pregnancy has been neglected. METHODS: A total of 7,872 newly married couples, enrolled between 1987 and 1988, were followed up until 1994-1995; only 2% were lost to follow-up. During face-to-face interviews, background and fertility-related data were collected. Chi-square tests and logistic regression were used to assess associations with unintended pregnancy. RESULTS: By three months after marriage, 461 couples had conceived; 57% of nonpregnant wives said that their preferred interval between marriage and conception was no more than three months. Twenty-one percent of pregnancies occurring between marriage and first birth were reported as unintended; 81% of these resulted from contraceptive failure. The majority of unintended pregnancies were carried to term; 13% were aborted. The younger the wife and the greater her desired interval between marriage and conception, the greater the likelihood that a pregnancy occurring before first birth was unintended. After first birth, 43% of couples experienced one or more unintended pregnancies, 98% of which were aborted in accordance with the one-child policy. The majority of these pregnancies occurred in the 12 months after first birth, when couples tend to rely on ineffective methods of contraception. The odds of having an unintended pregnancy after first birth were slightly elevated if at least one spouse desired a second child. CONCLUSIONS: Unintended pregnancies are common among married couples in Shanghai. Policies to reduce unintended pregnancies, and abortions, should focus particularly on postpartum contraception.