The solubility and diffusion coefficient of carbon dioxide in the biodegradable polymers poly(butylene succinate) and poly(butylene succinate-co-adipate) were measured at temperatures from 323.15 to 453.15 K and pressures up to 20 MPa. The solubilities iii the polymer's molten state increased linearly with pressure and decreased with temperature. Solubilities could be correlated to within 2.2% by the Sanchez-Lacombe equation of state in conjunction with a temperature-dependent interaction parameter. The Sanchez-Lacombe equation of state was also found to be applicable to the correlation of solubilities in the semicrystalline state. The interaction parameter determined from fitting the solubility was inversely proportional to temperature. The diffusion coefficients of carbon dioxide showed a weak concentration dependence and had an order of magnitude of 10(-9) m(2)/s in the molten state. The diffusion coefficients were correlated with the free-volume model of Kulkarni and Stern.