Melt-state polymerization of synthesized cyclic phenylene sulfides is reported. Fourier transform infra-red (FT i.r.) spectroscopy is used to follow the crystallization as a function of time. Optical microscopy is used to examine the morphology during polymerization. The resulting polymer is compared with commercial poly(phenylene sulfide) using differential scanning calorimetry (d.s.c.), (FT i.r.) spectroscopy, density measurements and optical microscopy. The glass transition temperature and crystallization parameters as a function of the reaction temperature are obtained by (d.s.c.) and related to the degree of polymerization. The effect of thermal treatment with and without carbon fibres is also examined. Curing of the cyclic phenylene sulfides is also examined at various temperatures. Densities of the polymer and cyclics are compared.