A semiempirical mathematical model has been developed to predict inhibitor efficiency for barium sulfate scale control in industrial processes. This model can be used for selecting effective inhibitors and determining the minimal effective concentration needed for a given system. The model incorporates experimental data of the nucleation and inhibition kinetics. Specifically, the induction period in the presence and absence of scale inhibitors has been measured experimentally and inputted into the model : C-inh = (1/b) log[t(inh)/t(0)], where C-inh is the inhibitor concentration, t(inh) is the inhibition time (e.g., 20 min), to is the nucleation induction period of the scaling mineral crystal, and b is the inhibitor efficiency. The inhibition kinetics of barium sulfate nucleation with bis(hexamethylene)triaminepenta(methylenephosphonic acid) (BHMTPMP) and several other polyphosphonate and polyacrylate inhibitors have been measured. Many factors which are important to nucleation and inhibition kinetics, such as the degree of supersaturation, temperature, and solution pH, have been included in the inhibitor model. The model prediction for barium sulfate scale control was in good agreement with laboratory observations and field experience.