A procedure for wet digestion of fish tissue that utilizes nitric, sulfuric, and perchloric acids can digest 1 g of fish tissue in approximately 45 minutes. This procedure allows for the preparation of large numbers of samples and is suitable for the analysis of Cd, Cu, Mn, Zn, and probably other heavy metals by atomic absorption spectroscopy. The method eliminates the problem of clogging of the aspirator tube of the atomic absorption unit.