Physical, chemical, and enzymatic means for the desorption of micro-organisms from granular activated carbon (GAC) were assessed. Data indicate that homogenization at 16,000 rpm for 3 min at 4 C with a mixture of peptone (0.01%), Zwittergent 3-12 ( times 10 to the minus 6 power M) ethyleneglycol-bis-(Beta amino-ethyl ether)-N,N sup 1-tetra acetic acid (EGTA times 10 to the minus 3 power M) and Tris buffer (times 10 to the mius 1 power M, pH 7.0) was effective in desorbing both HPC and coliform bacteria from GAC particles. This method was also effective in removing Escherichia coli from GAC. Four media were tested for their ability to enumerate desorbed HPC bacteria. R2A medium incubated at 18 C for 7 days provided maximal counts.