Biochemical studies on the oxygen uptake by bovine gingival ephitelium slices and mitochondrial fraction were made using the classical manometric technique of Warburg. The integrity of the structure of bovine epithelium mitochondrial fraction was controlled by electron microscopy. The oxygen quotients for bovine gingival epithelium slices were similar to that reported by others. Only succinate (QO2=L05) and malate (QO2=O.89) were oxidized by slices. The mean oxygeti quotient endogenous for mitochondrial fraction was 1.46; for succinate and malate were 4.40 and 3.00, respectively. No evident effects of diphenylhydantoin on oxygen consumption either by bovine gingival epithelium slices or mitochondrial fraction were observed.