Whole cells of Micrococcus lysodeikticus ATCC 4698 bound approximately 2–4 per cent of phenol-14C (P-14C), 20 per cent of 2,4-dichlorophenol-14C (DCP-14C), and 30 per cent of p-tert-amylphenol-14C (PTAP-14C) when exposed to the latter in trace amounts. Protoplasts bound approximately 20 per cent less, respectively, of each of the phenol derivatives. With increasing pH (from 4.9 to 9.6), whole cells bound decreasing amounts of DCP-14C, but binding of P-14C and PTAP-14C was relatively constant over the same pH range. Human serum decreased binding of DCP-14C and PTAP-14C by M. lysodeikticus cells and a similar effect, although less marked, was found with crystalline human serum albumin. The decrease was proportional to protein concentration. Human serum γ globulin in the same concentration as serum albumin did not reduce binding of the labeled phenols to the bacterial cells while a sonic disintegrate of M. lysodeikticus cells caused some reduction in binding. Whole cells of Micrococcus lysodeikticus ATCC 4698 bound approximately 2–4 per cent of phenol-14C (P-14C), 20 per cent of 2,4-dichlorophenol-14C (DCP-14C), and 30 per cent of p-tert-amylphenol-14C (PTAP-14C) when exposed to the latter in trace amounts. Protoplasts bound approximately 20 per cent less, respectively, of each of the phenol derivatives. With increasing pH (from 4.9 to 9.6), whole cells bound decreasing amounts of DCP-14C, but binding of P-14C and PTAP-14C was relatively constant over the same pH range. Human serum decreased binding of DCP-14C and PTAP-14C by M. lysodeikticus cells and a similar effect, although less marked, was found with crystalline human serum albumin. The decrease was proportional to protein concentration. Human serum γ globulin in the same concentration as serum albumin did not reduce binding of the labeled phenols to the bacterial cells while a sonic disintegrate of M. lysodeikticus cells caused some reduction in binding.