This investigation looked at the influence of high phenol concentrations (1000-1500 mg/l) on the growth yield of phenol degrading organisms in batch culture. The yield coefficient varied from 0.16 to 0.27. These values are considerably lower than those determined by others at lower phenol substrate concentrations. Although the conversion efficiency to biomass was low, the removal of phenol in terms of COD in the batch cultures was high (93.6% average). Present results did not show a relationship between yield and specific growth rate over the range 1000-1500 mg/l phenol. More work is required over a wider range of substrate concentration. With increasing phenol concentrations, the specific growth rate declined, consistent with Haldane inhibition kinetics.