In this study, the three-phase, hydrate-liquid-vapor (H-L-w-V), equilibrium conditions of the R22 (CHClF2) gas hydrate in aqueous solutions containing sucrose, glucose and lactic acid were experimentally determined at pressures ranging from 0.15 to 0.9 MPa with temperatures between 274 to 290 K. The experiments were performed at concentrations of 20 and 40 wt.% of sucrose, glucose, and lactic acid in each aqueous solution. It was found that the organic materials (sucrose, glucose and lactic acid) exhibited a substantial inhibiting effect similar to electrolytes and methanol. At the same concentration of each organic solute, the lactic acid showed a large effect on the inhibition of R22 hydrate formation. A thermodynamic model for the prediction of gas hydrate equilibria and the inhibition effect of organic solute was also developed. The three-phase H-L-w-V equilibria were calculated by using the Redlich-Kwong-Soave equation of state with a modified version of the Huron-Vidal mixing rule. The results of the predicted three-phase equilibrium conditions for the R22 hydrate formation in aqueous solutions containing sucrose, glucose and lactic acid were in good agreement with the experimentally determined equilibrium data. (C) 1998 Elsevier Science B.V. All rights reserved.