Previous studies suggest that hormonal factors modulate the natural course of psoriasis in women. However, the association of hormonal factors with psoriasis risk has not been assessed using prospective data. We carried out a thorough prospective analysis on the topic in 163,763 women in the Nurses' Health Study I and II. Participants provided information on age at menarche, parity, menopause status, and exogenous hormone use (oral contraceptive and postmenopausal hormone therapy) over the follow-up. We ascertained 1,253 incident psoriasis cases over 2 million person-years. Psoriasis risk appeared to be higher in women with always irregular menstrual cycles in adulthood (multivariate-adjusted hazard ratio=1.32, 95% CI: 1.01-1.73, compared with regular cycles) and surgical menopause (hazard ratio=1.19, 95% CI: 1.01-1.40, compared with natural menopause). Hormone therapy had suggestive but insignificant associations with psoriasis risk. Our results suggest little evidence for hormonal factors and risk of psoriasis in women that need further investigation.