Several well-established procedures for the isolation of enzymes involved in glycogen metabolism have been modified such that all the enzymes can now be isolated from the same muscle preparation. The purified proteins are the catalytic subunit of cyclic AMP-dependent protein kinase, its thermostable inhibitor, glycogen phosphorylases a and b, and phosphorylase kinase. Phosphorylase kinase is separated by acid precipitation of the muscle extract. The other proteins are purified from the acid supernatant by chromatography on DEAE-cellulose. Further purification of each protein to homogeneity is then achieved using previously described methods. The proposed protocol saves sample tissue, and considerably reduces the work involved in obtaining muscle samples.