A detailed chemical study is being made of the lipid composition (including individual fatty acids) of human testicular tissue obtained at orchiectomy (patients with prostatic cancer) or at autopsy. The biosynthesis of fatty acids from various labeled precursors is being studied as is the interconversion of long chain fatty acids. Analyses of whole tisse will be supplemented with findings in subcellular fractions. Findings of lipid composition and metabolism are supplemented with histological studies of the tissue relative to spermatogenesis.