The lupine aphid,Macrosiphum albifronsEssig, occurs throughout southwestern British Columbia onLupinus arcticusS. Wats. andL. polyphyllusLindl., and less frequently onL. sericeusPursch. It is parasitized by four species of Aphidiidae:Aphidius lupiniLiu,Ephedrus californicusBaker, and two unidentified species ofPraon.Percentage of parasitism varied seasonally and between collecting sites.A. lupiniwas the most common and widespread parasite; it killed an average of 5.2, 7.6, and 9.0% of secondo-, third- and fourth-instar aphids, respectively, over the season as a whole. A fungal pathogen,Entomophthorasp., caused ca. 60% mortality among third- and fourth-instar aphids during rainy periods in late spring and late summer.A. lupiniis considered as a potential agent for biological control of the lupine aphid in England.