Seasonal variations of lamprey hepatocyte endogenous respiration during spawning migration (November–May), when the animals are starving, were determined. In winter, the respiration is decreased 2.5–3 times as compared with the respiration of early migrants in Autumn and markedly (about twice) increased again in Spring (April). The reasons for such regulation are discussed. The respiration responsible for ATP synthesis and proton leak and non-mitochondrial respiration in hepatocytes were determined in every season. The content of adenine nucleotides in hepatocytes of the autumn migrants was close to that of mammals. However, ATP concentration in Winter decreased markedly (ten times in individual animals). Isolation of viable cells at this period is possible only in the medium with pH 6.5. In Spring, the level of adenine nucleotides again reached the Autumn value. Weight characteristics and protein content of lamprey hepatocytes are about ten times lower than those of the mammalian ones. The mass of lamprey hepatocytes decreased by 30–40% at the period from early Spring to the spawn in May, most likely this decrease being due to the lipid expenditure.