Sex determination is the basis of systematic studies on human skeletal remains. In this paper, we explore the relative diagnostic efficiency of two methods employed to determine sex in mandibles from Médano Petroquímica site, Argentina. Techniques used were the angle of posterior inflexion of mandibular ramus and the traditional method using multiple morphological traits of the mandible. The sex was separatedly assessed by two trained technicians who applied three times eachone. Results show a greater consistency and a relative efficiency in the traditional procedure compared to the first one. We conclude that the Loth and Henneberg technique (1996) cannot reliably replace the traditional technique, at least not in the case of secondary burials considered. https://doi.org/10.22380/2539472X11