Parasitism of the stem and branch-boring moth Coleophora parthenica Meyrick (Lepidoptera : Coleophoridae), introduced into California for the biological control of Russian thistle, Salsola australis R. Brown (Chenopodiaceae) was studied in the Coachella Valley of southern California during 1985-1986. Eight parasitoid species were reared from overwintering larvae of C. parthenica, but none from the F-1 larvae, and just 2 individuals of one species from the F-2 summer generation. The level of parasitism of overwintering larvae was positively correlated with branch diameter, and ranged from 2% in the primary (main) branches to 45% in the tertiary branches int he spring 1985 sample, and from 2% to 19% in the spring 1986 sample, respectively. Rates of parasitism gt 20% were only found at sites with higher plant cover and chenopod diversity, but no other plant source or alternate hosts of the parasitoids of C. parthenica were found. The 2 dominant species, the solitary, hymenopterous ectoparasitoids, Norbanus perplexus (Ashmead) (Pteromalidae) and Eurytoma strigosa Bugbee (Eurytomidae), are both congeners of native parasitoids of C. parthenica in Pakistan. The 2 other species of parasitoids of C. parthenica in southern California for which other hosts are known are polyphagous and external on the larvae. No specialized endoparasitoid Braconidae, like those which dominate the native parasitoid complex in Pakistan and the U.S.S.R., have transferred to C. parthenica during its first 10 years in southern California.