Temperature-dependent development of a Czechoslovakian population of the parasitoidAphidius matricariaeHaliday was measured at eight constant temperatures between 11 and 31°C using the Russian wheat aphid,Diuraphis noxia(Mordvilko), as a host. Development rate from oviposition to emergence of adult wasps increased linearly with increasing temperature between 11 and 26°C. No adult wasps emerged from parasitized aphids at 31°C. Requirements for development from oviposition to adult eclosionwere 273.1 ± 5.9 degree-days above a threshold of 4.5 ± 0.4°C. These results are compared with previously reported data on temperature-dependent development of other populations ofA. matricariaeand the host,D. noxia.