The specific activity of alkaline phosphatase in soluble and mitochrondrial fractions from the black carpet beetle, Attagenus megatoma (F.) was age dependent. During larval development the lowest and the maximum specific activities for the soluble fraction were recorded in the 2- ancl 9-month-old larvae, respectively. The soluble fraction underwent a striking decrease with the onset of pupation. The specific activity of the mitochondrial fractions did not exceed that of the corresponding soluble fractions during the larval and the pupal development. Transition from the pupal to the adult stage was accompanied by an increase in the activities of both fractions. However, a decrease in the specific activity of soluble fraction was observed in 13-day-old adults