The status of thiamin, riboflavin and pyridoxine in 717 healthy children aged 1-60 months and 569 mothers aged 16-45 years attending a well-baby clinic in Bangkok were determined by using the erythrocyte enzymes, transketolase, glutathione oxidoreductase, aspartate aminotransferase and measuring the degree of stimulation with the coenzymes thiamin pyrophosphate, flavin adenine dinucleotide and pyridoxal phosphate respectively. Cut-off points for the upper limit of the normal ranges for the respective activation coefficients were established from the data obtained.