Objective To assess whether nutritional deficiency increases susceptibility to arsenic-related health effects. Design Assessment of nutrition was based on a 24 h recall method of all dietary constituents. Setting Epidemiological cross-sectional study was conducted in an arsenic-endemic area of West Bengal with groundwater arsenic contamination. Subjects The study was composed of two groups - Group 1 (cases, n 108) exhibiting skin lesions and Group 2 (exposed controls, n 100) not exhibiting skin lesions - age- and sex-matched and having similar arsenic exposure through drinking water and arsenic levels in urine and hair. Results Both groups belonged to low socio-economic strata (Group 1 significantly poorer, P < 0·01) and had low BMI (prevalence of BMI < 18·5 kg/m2: in 38 % in Group 1 and 27 % in Group 2). Energy intake was below the Recommended Daily Allowance (set by the Indian Council of Medical Research) in males and females in both groups. Increased risk of arsenical skin lesions was found for those in the lowest quintile of protein intake (v. highest quintile: OR = 4·60, 95 % CI 1·36, 15·50 in males; OR = 5·62, 95 % CI 1·19, 34·57 in females). Significantly lower intakes of energy, protein, thiamin, niacin, Mg, Zn and choline were observed in both males and females of Group 1 compared with Group 2. Significantly lower intakes of carbohydrate, riboflavin, niacin and Cu were also observed in female cases with skin lesions compared with non-cases. Conclusions Deficiencies of Zn, Mg and Cu, in addition to protein, B vitamins and choline, are found to be associated with arsenical skin lesions in West Bengal. Copyright © The Authors 2012.