Knowledge of particle-liquid mass transfer coefficient. (k(SL)) is important for a rational design of a solid-liquid/solid-liquid-gas stirred tank reactor (STR). Considerable efforts have been made by different investigators to study and Correlate the behavior of k(SL) in STRs for a variety of geometric and operating conditions. This review attempts to put together and analyze the information available in the literature on k(SL) in STRs systematically. Different approaches,used by researchers to correlate k(SL) are critically. discussed. The effect of system configurations (type of the impeller, D/T, and C/T), operating parameters, (impeller speed/power input, particle loading, and gas flow rate), and physical properties (d(P), D-m, mu, and Deltarho), on k(SL), have been discussed elaborately. Some new data for six-bladed impellers have been generated to determine the optimum geometric configuration and operating conditions for particle-liquid mass transfer in three-phase STRs. It is concluded that k(SL) in two-/three-phase STRs can be correlated reliably over a wide range of system configurations and operating:parameters, by a relative, particle suspension term, N/N-S(G). Scope and need for further studies. have been suggested.