OBJECTIVE: To estimate the prevalence of musculoskeletal diseases, especially osteoarthritis, rheumatoid arthritis, osteoporosis and lumbar disc herniation, in Korean adults. For arthritis and total musculoskeletal diseases, trend of the age-standardized prevalence rates were evaluated. METHODS: This study was based on the data obtained from the Korea National Health and Nutrition Examination Surveys (KNHANES) I, II and III, conducted in 1998, 2001 and 2005, respectively. KNHANES is a nationwide cross-sectional study using a stratified, multistage probability sampling design for the selection of household units. Annual self-reported prevalence and its confidence interval were estimated in adults aged over 19, using Health Interview Survey in KNHANES. All analyses were done using SAS 9.1 with "survey procedure" except for age-standardized prevalence rates for comparison prevalence rates of each survey. Age-standardized prevalence rates were calculated using a direct-method. RESULTS: The prevalence of musculoskeletal diseases was 144.6, 140.0 and 197.2 and the annual self-reported prevalence of arthritis was 117.9, 109.2 and 146.4 per 1,000 population in 1998, 2001 and 2005, respectively. In KNHANES III, osteoarthritis was the most prevalent disease of the musculoskeletal diseases for both sex. Fifty-eight percent of the over 65 year-old population had at least one musculoskeletal disease and it was higher in women with 73%. CONCLUSION: The prevalence of musculoskeletal diseases was high in Koreans with arthritis being the most prevalent. The prevalence of musculoskeletal disease correlated with low sociodemographic status.