³H-leucine incorporation and translation of ribosome-bound mRNA were examined in adipocytes, adipose and liver tissues of male Sprague Dawley and Fischer rats ranging in age from 1.5–24 months and 6.32 months, respectively. ³H-leucine incorporation into isolated fat cell protein and mRNA within polysomes, isolated from adipose and liver tissue homogenates, were translated in a liver pH 5 enzyme cell-free system. Protein synthesis and translation of ribosome-bound mRNA declined significantly with age in the liver and adipose tissue, by 40% at 18 months in Sprague Dawley rats, and by 50% at 24 months in Fischer rats. In the very old rats of both strains (24 to 32 months), there was a paradoxical enhancement (18.30%) in protein synthesis and protein synthetic activity of the ribosomes in adipose and liver tissues compared to the mature rats. This enhancement was associated with an apparent increase in fat cell number. The biphasic responses in tissue protein synthetic activity of the ribosomes coincided with a fractional shift from polysomea to monosomes. The paradoxical effects of extreme aging could relate to recruitment of newly differentiated, highly active adlpocytes in the fat depot. The recruitment may be triggered by cell enlargement associated with chronic obesity and/or extreme aging.