AIMS: To compare the levels of C-reactive protein (CRP) in a range of chronic disorders such as osteoporosis, asthma, diabetes, chronic bronchitis/emphysema, myocardial infarction, current oral infections, stroke, angina pectoris, hay fever, and fibromyalgia/chronic pain syndrome. METHODS: In all, 5,323 men took part in the first and second health screening of the Oslo Study in 1972/73 and 2000. Questionnaire information on medical history recorded at the second screening was used to identify men with relevant diseases. Serum samples collected in 2000 were stored for later analyses of CRP. In 2000 the men were aged 48-77 years. RESULTS: Men with self-reported myocardial infarction, asthma, diabetes, chronic bronchitis/ emphysema, osteoporosis or fibromyalgia/chronic pain syndrome had significantly elevated mean levels of CRP versus non-cases. Men with osteoporosis had the highest mean values of 6.53 versus 3.55 mg/l in participants without this disease. Cases of asthma also had an increased mean CRP level of 5.01 versus 3.47 mg/l in non-cases and in chronic bronchitis/emphysema the corresponding levels were 4.42 versus 3.59 mg/l. Men with diabetes had 4.53 versus 3.53 mg/l and men with myocardial infarction had 4.27 versus 3.59 mg/l. In fibromyalgia/chronic pain syndrome the values were 4.79 mg/l and 3.60 mg/l respectively. CONCLUSIONS: Elevated CRP levels were observed in elderly men in a number of chronic diseases, indicating a persistent inflammatory response. Mean levels varied according to the disease and indicated a baseline level in the individuals with a particular disorder. This is useful knowledge when CRP is used in the clinic for infection and inflammation status.