The prevalence of vitamin A deficiency in a nationally representative sample of children 12-59 months old in Panama was assessed using serum retinol levels and dietary indicators. The median serum retinol level found was 1.27 +/- 0.42 mumol/L (38 micrograms/dL); 6.0% of the study sample providing adequate blood specimens had levels below 0.7 mumol/L (20 micrograms/dL), indicating deficient vitamin A intake. The Panama City Metropolitan Area and the country's western region had the highest prevalences of low serum retinol levels (below 0.7 mumol/L in 9% and 6% of the study children, respectively), as compared to overall prevalences of 5% in the two other regions studied. Low serum retinol levels were significantly more prevalent among Indians in the study group (primarily Guaymí Indians) than among non-Indians (13% versus 5%). Dietary information provided by the study children's mothers showed that high risk of inadequate dietary vitamin A intake closely paralleled low serum retinol levels; specifically, the highest prevalence of dietary inadequacy was found in the western region, especially among the Indians. The Panamanian Government is currently increasing distribution of high-dose vitamin A capsules to Indian preschoolers in Chiriquí and Bocas del Toro Provinces.