The aim of this study was to analyze human skeletal remains from 13th—14th centuries burials discovered on the territory of the Lower Castle in Polotsk, Belarus. The article deals with the morphological characteristics of medieval urban population and skeletal stress indicators such as mortality and cribra orbitalia.
 According to most craniological characteristics, a series of male skulls from Polotsk of the 13th—14th centuries is similar to a sample of the medieval rural population of Polotsk land from burial mounds of the 11th—13th centuries. The differences relate to an increase in the cranial index in the later Polotsk series, which reflects the onset of epoch-making brachycephalization. In addition, Polotsk urban population differs from the rural population in a number of features characterizing the structural features of the facial skeleton (a higher face, a larger index of facial protrusion, a smaller protrusion of the nose). These differences can be genetically determined and indicate the participation of the alien component in the formation of Polotsk medieval population.
 The body length of adult men from Polotsk varies within 162—175 cm and averages 169.5 cm. The body length of adult women varies within 147—159 cm and averages 156 cm. Compared to the later Polotsk population of 17th—18th centuries, the medieval urban population was taller (2.5 cm in men and 2 cm in women).
 The average age of adult death in the studied group was 35.1 years. The average age of death for Polotsk women was 3 years less than for men.
 The group of Polotsk medieval population is characterized by relatively high frequencies of cribra orbitalia. Among adults, the indicator is present in 32.2 % of cases, among children — in 55.5 % of cases.
 Compared with the rural population of the 11th—13th centuries urban population of Polotsk of the 13th—14th centuries had higher mortality rates and increased incidence of cribra orbitalia, which indicates deterioration in general health in Polotsk urban population. The most probable causes of this phenomenon were, on the one hand, negative factors of urbanization, and on the other hand, the cooling of the climate, which began in Europe in the 14th century and led to deterioration in the living conditions of a significant part of the region’s population.