The effect of multivitamin supplementation on thiamin, riboflavin and retinol nutrition was studied in ten male chronic pediatric patients at Ramathibodi Hospital. MTV forte (Government Pharmaceutical Organization) was given 1 tablet daily for ten days and the effect was compared with the preceding ten-day control period. Anthropometric biochemical, clinical and dietary assessments were performed throughout the study. Biochemical assessments of vitamin nutrition at the beginning and the end of a 10-day non-supplementation period revealed multiple vitamin deficiencies in the subjects, though clinical manifestation was not seen. Hospital diets improved vitamin nutrition of some patients but most of them still showed subclinical vitamin deficiencies. Improvement of vitamin nutrition was clearly shown in most patients after MTV supplementation. Multiple vitamin supplements should be prescribed in high-risk patients since there was no definite pattern of vitamin deficiencies in various diseases and early detection of vitamin deficiency was difficult to perform. The dosage between 1-2 times of RDA was considered adequate in most of our patients.