To assess Fe intake, calculate the prevalence of inadequate Fe intake and identify food contributors to Fe intake during 2003 and 2008 in a population-based study, reflecting before and after the mandatory fortification of flour with Fe. Two cross-sectional population-based studies conducted in 2003 and 2008. Dietary intake was evaluated by 24 h recall and the Software for Intake Distribution Estimation (PC-SIDE) was used to estimate within-person variance and prevalence of inadequate Fe intake. The statistical analysis was conducted considering the complex survey design. São Paulo, Brazil. Adolescents, adults and elderly adults of both sexes, interviewed in 2003 (n 2386) and 2008 (n 1661). The Fe intake mean increased in all populations in the post-fortification period. A reduction of over 90 % was observed in the prevalence of inadequate Fe intake among men for all age groups analysed. When evaluating women, despite the substantial reduction (over 63 %), prevalence of inadequate Fe intake remained high (34 %) in those aged 19-50 years. Major food contributors to Fe intake before fortification were beans, beef, vegetables and dairy. There was an alteration in the contributors in the post-fortification period, with bread, beef, beans and biscuits as main contributors. The mandatory fortification with Fe significantly furthered the reduction in the prevalence of inadequacy, except among women of reproductive age, and changed the main contributors to this nutrient in the studied population. Therefore, monitoring of Fe addition in flour is essential to assess compliance to the fortified flour policy and to guarantee a safe Fe intake for all the population.