From 1985 to 1990, 372 red deer (Cervus elaphus) from southern Spain were examined for larvae of pharyngeal bot flies Pharyngomyia picta and Cephenemyia auribarbis. The infestation was related to age, sex and intensity of infection. Fawns and adult deer (more than 5 years old) had a significantly (P < 0.05) higher prevalence and intensity of infection than younger deer. Conversely, no significant difference has been noted between sexes. Ninety percent of deer were found to be infested. A simultaneous occurrence of both species was found in 23% of cases, with noticeable differences between prevalence and intensity of infection (measured in number of bots per head for each species). Quantitative overlapping between P. picta and C. auribarbis seems relative and their biological cycles did not overlap completely.