Plasma 25-hydroxy cholecalciferol (25-OH vitamin D) concentrations were measured in 31 adult Saudi Arabian women who presented with acute minor illness. Patients with chronic diseases, malignancy and overt metabolic bone disease were excluded from this study. The median plasma 25-OH vitamin D concentration was 6 ng/ml (range: 2-18 ng/ml). Only three subjects had a concentration within the normal range (10-55 ng/ml). Plasma 25-OH vitamin D concentrations were significantly lower in subjects living in apartments than in those living in villas or rural areas (P less than 0.02). When direct questioning was used to assess exposure to sunlight, plasma 25-OH vitamin D concentrations were significantly lower in those subjects whose average exposure was less than 30 min daily than those whose exposure was more than 30 min daily (P = 0.002). Our findings confirm the importance of inadequate exposure to sunlight in the aetiology of vitamin D deficiency. Social customs may contribute to this deficiency in spite of abundant sunshine. Direct questioning to assess the adequacy of sunlight exposure is an essential part of history taking in cases of suspected vitamin D deficiency.