A largely unresolved ecological issue concerns why normally rare parasites become common within reptile and amphibian populations. We gathered demographic data on incidence of infection and demographic consequences of a normally rare sarcophagid fly parasite (Lepidodexia blakeae) on a population of Green Anole Lizards (Anolis carolinensis). These sarcophagid flies primarily larviposit on adult male Green Anoles during the winter. Sampling by age and sex classes during two years (2003 and 2004) revealed that adult male anoles were infected at an unusually high rate (up to 16%) compared to other populations (only a few documented cases over the past 60 years) and relative to conspecific juveniles and females. Male anoles at Tulane exhibited high mortality compared to other nonparasitized populations, suggesting that parasitism negatively affects survivorship. Although the underlying cause of the high parasitism in the Tulane population remains unclear, several lines of evidence suggest that high and stressful levels of male competition may be a key factor.