The effect of lead on hepatic mitochondria and microsomes of chick embryo was studied with special attention to the role of lipid peroxidation in the manifestation of lead toxicity. Mitochondrial enzymes such as succinate dehydrogenase, cytochrome C oxidase and ATPase were found to decrease in a dose dependent manner upon lead administration. Further, mitochondrial cytochromes, microsomal cytochrome P-450 and heme levels were reduced considerably with concomitant increase of mitochondrial and microsomal lipid peroxides. In the present investigation an attempt has been made to correlate the lead induced lipid peroxidation, the loss of mitochondrial and microsomal hemoproteins and the inhibition of mitochondrial enzymes in chick embryo.