The aim of this study was to develop and validate a food frequency questionnaire (FFQ) to assess the folate intake of women of childbearing age (between 18 and 45 years). An FFQ containing 140 foods that have the potential to contribute significantly to folate intake was developed. The FFQ was pretested by comparing it with three-day food records completed by 20 women living in Vancouver, British Columbia. The 140-item FFQ overestimated mean daily folate intake (546 +/- 145 mg/day versus 385 +/- 151 mg/day with three-day food records); the two methods were not correlated (r = 0.359, p = 0.143). The FFQ was revised to better represent usual folate intake, and the 140 items were reduced to 81. The 81-item FFQ was validated with 17 women who completed the FFQ and a seven-day food record over four weeks. The mean daily folate intakes were 421 +/- 136 mg/day and 376 +/- 87 mg/day for the FFQ and the food records, respectively; the two methods were significantly correlated (r = 0.512, p = 0.036). This study resulted in a validated FFQ that can be used as an instrument to determine folate intakes in similar populations.