Gel formation and the melting of solutions of poly (γ-phenacyl L-glutamate) in DMP were investigated up to 40 wt% of polymer concentration. Two thermally reversible transitions were observed around 24°C and 55°C. The transition temperatures were almost independent of the concentration. The transition at 24°C was considered to be due to the collapse of the order in side-chain structures. The transition from gel into Isotropie or cholesteric liquid-crystal phase occured in the 50–60°C range, above which the gel rigidity and an X-ray reflection of about 40 A suggesting a complex phase disappeared.