Iron deficiency has been suspected to represent one of the possible causes of excessive hair loss in women. The aim of our study was to assess this relationship in a very large population of 5110 women aged between 35 and 60 years. Hair loss was evaluated using a standardized questionnaire sent to all volunteers. The iron status was assessed by a serum ferritin assay carried out in each volunteer. Multivariate analysis allowed us to identify three categories: "absence of hair loss" (43%), "moderate hair loss" (48%) and "excessive hair loss" (9%). Among the women affected by excessive hair loss, a larger proportion of women (59%) had low iron stores (< 40 microg/L) compared to the remainder of the population (48%). Analysis of variance and logistic regression show that a low iron store represents a risk factor for hair loss in non-menopausal women.