The kinetics of ethane hydrate decomposition was studied using an isothermal/isobaric semibatch stirred-tank reactor. The experimental set-up and procedure used was similar to that used by Kim, Bishnoi, Heidemann and Rizvi (1987), Chemical Engineering Science, 42, (1645-1653) with one major modification; the addition of an on-line particle size analyser. The experiments were conducted at temperatures ranging from 274.15 to 281.15 K and at pressures between 5 and 11 bar. A new mathematical model is developed to determine the rate constant of decomposition. The model accounts for the distribution of particle sizes in the hydrate phase when determining the intrinsic rate constant of decomposition. The effect of the rate of stirring on the rate constant was also investigated to establish the regime where mass and heat transfer effects were negligible. The data were then obtained to determine the intrinsic rate constant. It was found that the activation energy for ethane hydrate decomposition is 104 kJ/mol and the intrinsic rate constant of decomposition is 2.56 x 10(8) mol/m(2) Pa s.