Objective: To evaluate the long-term effects of a horticultural and nutrition education intervention in rural Tanzania. Design: A quasi-experimental post-test design was used. Setting: The research was carried out in 10 villages in Singida region, Tanzania. Subjects: Mothers and their children aged 6±71 months (n = 236) from an experimental (Ilongero) and control (Ihanja) area were interviewed regarding knowledge and practices related to vitamin A nutrition. Intake of vitamin A-rich foods by the children during the 7 days prior to the interview was recorded. Stools were examined for helminths and serum samples were analysed for retinol and C-reactive protein (CRP) (n = 146) for the children aged 12±71 months. Results: Knowledge and practices were more favourable to vitamin A intake in the experimental area than in the control area, and an increased frequency of intake of green leaves was associated with higher serum retinol values. The experimental area had lower mean serum retinol levels (13.7 mg dl , n = 71). One likely confounder was the higher helminth infestation in the experimental area (n = 75, 79%) than in the control area (n = 71, 49%) (P , 0.001). Children with helminths (n = 94) had a lower mean serum retinol level than those without (n = 52) (12.3 6 5 vs. 24 6 10 mg dl -1