This paper describes the prevalence and correlates of symptoms and health problems in pregnancy using data from a prospective population study in London. Data on the prevalence of 11 symptoms and 12 health problems were obtained at three points in pregnancy from a consecutive sample of 1513 white women. Relationships were examined between these symptoms and a range of psychosocial factors including social class, education, marital status, income, smoking, alcohol, caffeine, attitude to pregnancy and whether the pregnancy was planned. Most women reported nausea and breast tenderness in early pregnancy. Heartburn, backache, constipation and headaches were also common. The prevalence of symptoms tended to increase with gestation except for nausea and vomiting. Women with manual occupations, minimum education, low income, single marital status and unplanned pregnancy reported more of most symptoms except nausea which was associated with higher social status. A negative attitude to pregnancy was associated with more headaches but was unrelated to nausea. Women who smoked reported more 'nerves and depression' but less nausea. In general, nausea and vomiting showed a different pattern of associations from all other symptoms.