Angiostrongylus vasorum and Crenosoma vulpis infect the pulmonary arteries and airways, respectively, of red foxes (Vulpes vulpes). Both are widespread in Europe, but within North America, A. vasorum occurs only on the island of Newfoundland. During 2000–2002, 366 red fox carcasses were examined from six regions of Newfoundland for the purpose of determining the distribution of both parasites, effects on the condition of their host, and whether infection with one affects that of the other. Crenosoma vulpis occurred island-wide with a prevalence of 87% and mean (±SE) intensity of 230 ± 20.8. Young-of-the-year red foxes had more C. vulpis (260 ± 39.4) than yearlings (91 ± 31.2) or adults (78 ± 41.1) (χ2 = 25.72, df = 2, p < 0.001), and numbers of adult worm were weakly related to fecal output of first-stage larvae (r2 = 0.20, p < 0.001) but not to host sex or body-fat index. Angiostrongylus vasorum occurred only in southeast Newfoundland where prevalence was 56% and mean intensity was 72 ± 7.6. Its distribution may be limited by cold, as it was absent from areas with mean winter temperatures below –4 °C. Intensity of adult A. vasorum was not related to host age, sex, larval output, or measures of body condition. Although referred to as a heartworm, 88% of adult worms were actually found in the pulmonary arteries rather than in the right ventricle. Furthermore, there was no apparent association between infections with the two parasites (Gc[1] = 0.10) even though 40% of red foxes had dual infections.