For modeling nitrification in wastewater treatment processes it is necessary to determine the dependence of the maximum specific growth rate (μ A) of nitrifying bacteria on temperature and pH. A functional relationship for the simultaneous dependence of the effective maximum specific growth rate (μ A) minus the decay coefficient, b A) on temperature and pH, obtained from theoretical arguments, was verified via batch experiments with sludge from a local wastewater treatment plant. The parameters for the functional relationship were determined from the experimental data using a nonlinear regression scheme. An optimum pH of approx. 7.8 was determined and the effective maximum specific growth rate was found to be a monotonically increasing function of temperature in the range of 15–25° C.