Marques MD, Bjertness E, Eriksen HM. Caries prevalence of young adults in Oslo, Norway, and Porto, Portugal. A comparative analysis. Acta Odontol Scand 1994;52:111–115. Oslo. ISSN 00014357The purpose of the present study was primarily to establish the oral health status of young adults in the area of Porto, Portugal. The assessment is based on a random sample of 30–to 39-year-olds with criteria identical to those of a Norwegian study of 35-year-olds. This makes it possible also to present a comparative analysis of the caries prevalence in Oslo, Norway, and Porto, Portugal. The results indicate lower DMF scores among the Portuguese (DMFS = 46.2) than the Norwegian (DMFS = 85.0) adults. The difference is primarily due to a greater number of filled surfaces among the Norwegians (FS = 59.7) than the Portuguese (FS = 4.4). However, carious surfaces are more prevalent among Portuguese than Norwegian adults (DS = 9.2 versus DS = 3.3). Both among Portuguese and Norwegian adults, oral hygiene and dental visits seem to play an important role with regard to the prevalence of decayed surfaces. Decayed surfaces were more prevalent among men than women, and a correlation between social status and prevalence of decayed surfaces was present in both societies.