A microcalorimetric technique based on bacterial heat-output was explored to evaluate the toxic effect of different diphenol species on the growth of Escherichia coli (E. coli). Power-time curves of the growth metabolism for E. coli in the presence of different diphenol species were studied using a multi-channel microcalorimetric system with an ampoule method at 37 degrees C, The growth rate constant (k), generation time (t(G)), inhibitory ratio (I), half-inhibitory concentration (IC50) and the total thermal effect (Q(T)) for E. coli were obtained. The results show that catechol and hydroquinone are more toxic to E. coli than resorcinol. In all cases, the growth rate constants of E. coli (in log phase) decreased as the concentrations of these diphenols increased. Among these diphenols species, catechol was found to be the most poisonous species at an IC50 of 323.5 mu g/mL against E. coli. Hydroquinone exhibited moderate virulence with an IC50 of 1196 mu g/mL and resorcinol had the lowest toxicity with an IC50 of 2113 mu g/mL. The microcalorimetric bioassay can be a quantitative, inexpensive, and versatile method for acute cellular toxicity study.