Highly crystalline, rapidly crystallizing thermoplastic compositions containing:a) 70-99.5% by weight of a polyphenyl sulphide having a melt viscosity of at least 5 Pas (measured at 306.degree. C. and at a shear stress of 10.sup.2 Pa) andb) 0.5-30% by weight, relative to a) and b) of an oligomeric ester having at least two repeating ester monomeric units and a maximum molecular weight, expressed as a number average, of 6000.