Abstract The influence and possible negative impact on sinus health of living conditions in rural and urban environments in Viking Age (AD 800–1050) and Early Medieval Sweden (AD 1050–1200) is investigated. Skeletal samples from 32 rural settlements in the Mälaren Valley (AD 750–1200) and burials in the nearby proto-urban port of trade Birka (AD 750–960) are examined. Based on the diagnostic criteria for maxillary sinusitis used in earlier studies, the results show that there is no significant difference in the prevalence of signs of sinusitis between the two materials (i.e. the Mälaren Valley versus Birka). Consequently, this provides no evidence that living in a proto-urban environment had a negative impact on sinus health. However, when compared with previously studied samples from the early medieval town Sigtuna, dated to AD 970–1100, the populations of the Mälaren Valley and Birka show significantly lower frequencies of bone changes interpreted as chronic maxillary sinusitis (95%, 70% and 82% respectively). This implies that the urban environment of Sigtuna could have led to impaired sinus health. There is also a significant difference between males and females in the Birka material, in which more females (100%) than males (68%) were affected. A gender based differentiation in work tasks is suggested by this, or exposure to environmental risk factors that affect sinus health. No difference between males and females could be detected in the samples from the Mälaren Valley and Sigtuna.