C57B1/6J male mice of different ages were treated with clofibrate (CPIB) and the effect of the drug upon liver and kidney catalase activity was determined. Enzyme activity in hepatic tissue was induced 2.5-fold in all age groups from similar maintenance levels of activity. There was no age-related lag in enzyme induction, nor were there any age-related differences in the kinetics of induction. This increase in enzyme activity was accompanied by a marked hepatomegaly in all treated animals. CPIB had no effect upon catalase activity in the kidney of young animals. The decreased enzyme activity which is always observed in aging mice is, however, unexpectedly restored to young levels after treatment of old animals with CPIB. These results are reviewed in the context of the Orgel error hypothesis from which it is concluded that the results of this study offer no support for the Orgel hypothesis.