Study objective: To assess the association between lifetime socioeconomic position and onset of perimenopause. Design: Prospective cohort study. Setting: Boston, Massachusetts. Participants: 603 premenopausal women aged 36-45 years at baseline who completed a cross sectional survey on childhood and adult socioeconomic position. Main outcome measures: Time to perimenopause, defined as time in months from baseline interview to a woman's report of (1) an absolute change of at least seven days in menstrual cycle length from baseline or subjective report of menstrual irregularity; (2) a change in menstrual flow amount or duration; or (3) cessation of periods for at least three months, whichever came first. Main results: Incidence of perimenopause was 1.75 times higher (95%Cl 1.10 to 2.79) and median age at onset was 1.2 years younger (44.7 v 45.9 years) for women reporting childhood and adult economic distress compared with women reporting no lifetime economic distress. After adjustment for age, race/ethnicity, age at menarche, parity, oral contraceptive use, family history of early menopause, depression, smoking, and body mass index, the association weakened (incidence rate ratio (IRR)=1.59; 95%Cl 0.97 to 2.61). Inverse associations were observed for most, but not all, measures of educational level. Measures of current household income were not associated with risk of perimenopause. Conclusions: This study suggests that adverse socioeconomic conditions across the lifespan, when measured in terms of economic hardship and low educational attainment, may be associated with an increased rate of entry into perimenopause.