Male and female albino mice were fed on maize (control) and gari (a dried cassava product) based diets for 5 weeks. Liver mitochondrial fractions were assayed for succinate dehydrogenase and Cytochrome C oxidase activities. There was an overall reduction in the activity of the two enzymes studied throughout the experiment. The reduction in activity was pronounced in Cytochrome c oxidase. Kinetic studies of succinate dehydrogenase showed an apparent increase in the Km of the gari fed animals-further supporting that inhibition took place. There was also a reduction in the mitochondrial respiratory control ratio (RCR) for the gari fed mice. The percentage reduction in RCR increased from 4.4% in the 2nd week to about 45% in the 5th week.