Thiamin status and biochemical indices of malnutrition and alcoholism have been studied in groups of settled !Kung San living in the northern Kalahari Desert of Namibia. One third of the men and 20% of the women had low red cell thiamin concentrations. Raised serum gamma glutamyl transferase (gamma GT) activities were present in 30% of the men and 11% of the women. gamma GT activities were negatively correlated with red cell thiamin concentrations (r = -0.321, P less than 0.01). Raised mean corpuscular volumes were observed in over half the subjects. Anaemia was rare. Plasma protein and albumin concentrations were satisfactory. Cholesterol concentrations were relatively low (mean 4.1 mmol 1-1). The present results identify a high prevalence of thiamin deficiency in settled !Kung San, and suggest that alcohol abuse is the main contributory factor.