Myxosporida inhabiting Coryphaenoides abyssorum, C. leptolepis, C. pectoralis, C. acrolepis and C. filifer from off central and northern California, Oregon, and Washington are surveyed. Eight genera of myxosporidans, representing 5 families, were recovered from host gall bladders, urinary bladders, urinary ducts, or kidney tubules. Myxoproteus abyssets sp. n. in the urinary bladder and ducts of C. abyssorum, and Leptotheca atmatura sp. n. in the urinary bladder and kidney tubules of C. pectoralis and C. leptolepis are described. Myxidium coryphaenoidium is the most common myxosporidan parasite, inhabiting 8 species of macrourids from the Atlantic and Pacific oceans. In terms of numbers of parasite species, Myxosporida in macrourid fishes from benthic or benthopelagic environments are at least comparable with those in families of fishes from shoreline habitats. The study of host-parasite relationships in the deepsea environment has received little attention, primarily due to technical difficulties in securing large numbers of undamaged hosts that could be subjected to experimental and observational studies (Noble, 1973). This paper deals with protozoan parasites of the order Myxosporida (including two new species) inhabiting fishes of the family Macrouridae from the northeastern Pacific. A comparison with Myxosporida in macrourids from south of Point Reyes, California, and from the North Atlantic will be made. It is hoped that such studies will lead to a fuller understanding of the role of parasitism in the biological organization of the deep benthos. Macrourid fishes have recently been shown to harbor a large variety of myxosporidan parasites (Yoshino and Noble, 1973a, b). Some of these parasites (e.g., Ceratomyxa hokarari Meglitsch, 1960) appear to exhibit narrow host specificities, while others (e.g., Myxidium coryphaenoidium Noble, 1966) are widely distributed in many different macrourids independent of geographic location or depth. MATERIALS AND METHODS All autopsies were performed on alcoholor formalin-preserved fishes, with the exception of frozen Coryphaenoides abyssorum from central California. To reduce chances of contamination by Received for publication 15 November 1973. * This investigation was supported in part by National Science Foundation Grant No. GA 34144 to Dr. E. R. Noble. t The order of authorship was determined by the flip of a coin. protozoa from other organs, gall bladders, urinary bladders, and kidneys were isolated in screw-top vials prior to detailed microscopic examination performed at the University of California, Santa Barbara. Examination procedures are described in Yoshino and Noble (1973a). Host collection data and autopsy dates are given in Table I. Dimensions of Myxosporida are in microns.