The thermal and dielectric properties of poly(3-hydroxybutyrate) in dimethylformamide at a concentration of 10 gl(-1) have been investigated. This system shows a gel-sol transition as the temperature is raised from 25 to 90 degrees C. Two endothermic peaks are revealed by differential scanning calorimetry at 70 and at 85 degrees C respectively, which pair with two discontinuities in the electrical conductivity and in the permittivity when the sample undergoes annealing. A description of the observed process in terms of melting of microcrystalline domains is presented.