The prevalence of obstructive lung diseases is increasing in Scandinavia and worldwide. The reasons for this are not known. The prevalence varies between countries but also between different areas within the same country. In northern Europe a north-south gradient and also an east-west gradient have been proposed. To our knowledge this is the first comprehensive epidemiological study concerning obstructive lung diseases and respiratory symptoms in the southern part of Sweden. The prevalence of bronchial asthma, chronic bronchitis/emphysema, respiratory symptoms, smoking habits and medication in a random sample of 12,071 adults aged 20-59 years was assessed in a postal survey with a slightly modified questionnaire previously used in central and northern Sweden (the OLIN Studies). The questionnaire was based on the British Medical Research Council (BMRC) questionnaire. We also compared the prevalence figures of asthma found in the postal survey with those reported in the medical records in a part of the study area. After two reminders, the response rate was 70.1% (n = 8469); 33.8% of the responders were smokers. Among younger (20-39 year age group) individuals, smoking was most common in women, whereas in those aged 40-59 years, smoking was more common in men. In all, 469 subjects (5.5%) stated that they had asthma, 41.6% of whom reported a family history of asthma compared to 15.9% of the study sample not reporting asthma. Of all subjects reporting asthma, 60.1% (n = 282) answered that they used asthma drugs. Inhaled steroids were used by 20.7%. Chronic bronchitis and/or emphysema was reported by 4.6% (n = 392), 28.6% of whom reported a family history of chronic bronchitis or emphysema compared to 6.8% of the study sample not reporting chronic bronchitis. The most common respiratory symptom in the study population was 'phlegm when coughing' reported by 15.1% (n = 1279). Our data show a prevalence of self-reported asthma of 5.5% compared with 7% reported by Lunbäck et al. in northern Sweden, which indicates a north-south gradient.