The transport properties of carbon dioxide, water, and different organic solvents in bacterial poly(3-hydroxybutyrate)(PHB) at 30 degrees C were investigated. CO2 sorption was measured by the gravimetric method using a recording microbalance at subatmospheric pressures. Results were adequately interpreted in terms of Henry’s law. Organic solvent and water permeabilities for both vapors and liquids were measured using a gravimetric cell. The data were interpreted in different terms depending on the units in which permeability was measured. Most of the solvent-polymer systems showed the typical time-lag plot, but in liquid permeation experiments, some anomalous behaviors were observed, with a transient period of rapid permeation at the beginning of the experiment before reaching the steady state. The transport properties of PHB were compared with those of other polymers, either from synthetic or biodegradable origin.