We examined seasonal prevalence of a haematozoan parasite (Haemoproteus velans) of the Red-bellied Woodpecker (Melanerpes carolinus) in the Apalachicola National Forest, northern Florida. We also investigated how infection with H. velans was associated with host mass, body condition, and overwinter survival. Analysis of blood smears taken from individual woodpeckers between May 2000 and July 2001 indicated that prevalence of H. velans peaked in July 2000, at ∼80% of individuals sampled, decreased to 0% in January and February 2001, and peaked again in July 2001, at ∼50% of individuals. Infection with H. velans was associated with low mass and poor body condition in males. Infection showed no association with female mass. In addition, infection with H. velans showed no relationship with overwinter survival. Our data reemphasize the importance of considering seasonal variation in parasite prevalence during testing for haematozoa. In addition, our data suggest that, although infection with H. velans is associated with poorer host condition, it does not negatively affect host survival.