The purpose of this paper is to examine the thermodynamics of physical gelation by presenting some results gathered on gels of stereo-regular poly hydroxybutyrate (PHB). The investigation has been carried out in dilute solutions mainly by high sensitivity scanning calorimetry through the use of two solvent systems. Gels were formed under several different experimental conditions to clarify the thermo-reversibility of the gelation-dissolution process. Some peculiarities of the polymeric features in the gel phase rue discussed in view of the recent assessment of the implication of chain stiffness as the triggering factor for gelation versus crystallisation.