Polyhydroxybutyrate is a natural polymer that undergoes secondary crystallisation rendering the material brittle. This brittleness problem can be reduced by using a plasticiser. In this study, the influence of the solvent, (chloroform, acetone and toluene) as a plasticiser, on polyhydroxybutyrate was investigated. The polyhydroxybutyrate crystalline and amorphous FT-IR bands in the 950-1850 cm(-1) region were studied. No band change was identified between the different solvent systems rendering the conclusion that the solvent is not an influencing factor to PHB's crystalline and amorphous regions. Hot stage optical microscopy was also employed to further substantiate the FT-IR studies. However, a distinct and marked change between the solvents and pure PHB became evident. The growth rate decreased for all solvents compared to the homopolymer indicating a non-plasticising effect.