Measurements on the effect of crystallization temperature on the crystallinity, long period and unit cell dimensions of P(HB/HV) copolymers with 0-27% HV crystallized isothermally at 23, 52 and 81 degrees C are presented. The crystal composition has been estimated from the unit cell expansion and the relationship between crystallinity and density. The amount of cocrystallization of HV in the PHB crystal structure is found to decrease as the crystallization temperature is increased : the amount of HV in the crystals formed at 81 degrees C is reduced to 2/3 of the value for crystallization at room temperature. The results are consistent with cocrystallization being an effect of the kinetics of crystallization which becomes less significant as equilibrium crystallization conditions are approached.