Of the 1-year-old sockeye (Oncorhynchus nerka(Walbaum)) smolts migrating from Babine Lake in 1952 and 1953, in each year about 35% were infected with the cestodeEubothrium salvelini(Schrank, 1790) and 20% by the nematodePhilonema oncorhynchiKuitunen-Ekbaum, 1933. Six to 7% of the smolts harboured both parasites. Fish infected by cestodes only or cestodes and nematodes were significantly smaller than uninfected fish or those with nematodes only. This indicates that the cestode infection retards growth. Nematode-infected smolts were significantly larger than the uninfected individuals in 1952 but not so in 1953.