Prevalence and intensity of parasitism by oestrid larvae in the Spanish ibex Capra pyrenaica were determined for a period of 2.5 yr in Sierra Nevada Natural Park, southern Spain. The most relevant result of this study was to find Oestrus caucasicus parasitizing this ungulate in a geographical location far from its previously known distribution, e.g., the Caucasus mountain range and central Asia. Larvae were found within 74% of the heads examined (n = 180). Prevalence was higher in females and in older animals. Lowest prevalence occurred during the summer months. The mean intensity (+/- SD) was 25.4 +/- 27.3 larvae and was similar in both host sexes. The number of larvae increased with host age and reached the highest intensities in winter, during December and January.