['To assess the relation of socio-economic status to respiratory symptoms common in asthma and chronic bronchitis, and to compare risk factors for these symptoms between three neighbouring countries.', 'A postal survey was performed in 1996 as a part of comparative studies in Finland, Sweden and Estonia (the FinEsS studies). A random sample of 58,661 subjects aged 20-64 years were invited, of whom 44,483 participated.', 'Respiratory symptoms were most prevalent among manual workers, who were at significantly increased risk for chronic respiratory symptoms. The same pattern of increased risk appeared when the analyses were made among non-smokers only: for recurrent wheeze, manual workers in industry yielded an OR of 1.91 (95%CI 1.62-2.24) and in the service sector an OR of 1.50 (95%CI 1.27-1.78). The corresponding figures for chronic productive cough were 1.45 (95%CI 1.22-1.71) and 1.20 (95%CI 1.02-1.42), respectively. Risk factor profiles for respiratory symptoms were similar in Finland, Sweden and Estonia, except for gender differences in Estonia.'] Is low socio-economic status a risk factor for respiratory symptoms : a comparison between Finland , Sweden and Estonia?