Two hundred and eleven Indian skulls originating from medieval times, South of Peru, were studied in respect to variability of the mastoid emissary. Occurrence and localisation of the external orifice of the mastoid emissary were studied in three distinct and well-separated populations, living in the three different places: Villa el Salvador, Tablada de Lurin and Paracas. Most of the skulls presented considerable degree of artificial deformation. External orifice of the mastoid emissary was multiple in most of the skulls, especially in Villa el Salvador and Paracas populations. Mastoid emissaries in Indian were situated generally higher than in European, especially regarding the Paracas population. Significant sex differences were present in this material, regarded as a whole (summarized results for the three populations), what is in agreement with previous observations on European skulls. It indicates that even in cases of relatively deep deformation, some characteristic features of sex dimorphism of the human skull are noticeable. Additionally, the three studied populations, which were well separated from each other and lived alone, differed significantly regarding localization of the mastoid emissaries.