SummaryThe distribution of cases of rheumatoid arthritis and ankylosing spondylitis among the different central hospital districts in Finland was studied in the light of health insurance statistics for the period January—June 1965. It was found that for 0.6 per cent of the people over 15 years of age the drug treatment was totally compensated for because of rheumatoid arthritis. The corresponding figure for ankylosing spondylitis was 0.01 per cent. Compared with frequencies of rheumatoid arthritis and ankylosing spondylitis previously published it was possible to state that about 20 per cent of cases of rheumatoid arthritis and 5 per cent of those of ankylosing spondylitis have had the cost of drug treatment totally covered.