Discolored and normal areas in the enamel of eleven primary teeth from children born to diabetic mothers were analysed with ion probe technique. These teeth were compared with four teeth from children born to healthy mothers. Fourteen different mass numbers were recorded. The affected areas showed a proportionally higher content of organic material, but the differences in recorded values reached statistical significance only in the postnatal enamel. The study revealed a considerable biological variation in the chemical composition of deciduous tooth enamel. The brown areas may be partly related to variation in physical properties.