All women aged 15-45 years who are permanent residents in the study areas will be eligible for recruitment into the trial. They will be identified from existing databases. Permanent residence is defined as having been resident in the area for the three months preceding the start of recruitment, with intention to remain in the study area for the following 12 months. There will be no exclusions to participation, except for women who have nightblindness or other signs of VAD. These, and any women who develop VAD in the course of the study will be treated according to current IVACG recommendations (IVACG, 1997). They will continue to be followed, but will be given vitamin A and considered separately in the analysis. Continuous recruitment will be done for women who migrate into the study area, or those who become eligible by age as the study progresses. Allocation to treatment will be determined by the cluster of residence.