Changes in the specific activity of alkaline phosphatase in the normal and denervated skeltal muscle have been studied both histochemically as well as biochemically for a maximum period of 8 weeks of its postnatal development. In the normal muscle, a heterogenous population of fibres with respect to the enzyme distribution is observed. Relatively higher levels of enzyme in the denervated muscle and also the proliferation of extrafibillar connective tissue in the diseased muscle show its specific association with the lytic processes.