We studied the epidemiology of bone and joint tuberculosis (TB) in Denmark during the period 1993-1997, using data in the national Danish TB register. We found 95 cases, accounting for 4% of all tuberculosis cases and 15% of extrapulmonary cases, giving a mean annual incidence of 0.4 per 10(5) in the period. 26 cases were found among native Danes (3-8 cases per year) with a median age of 66 (10-92) years and giving a mean annual incidence of 0.1 per 10(5). Among immigrants, an increasing number of cases of bone and joint TB were diagnosed, increasing from 5 in 1993 to 28 in 1997, giving a total of 69 cases with a mean age of 35 (11-75) years and a mean annual incidence of 4 per 10(5) in the period. The spine was affected in half of the cases. 28 patients had active TB elsewhere in the same period. In most patients, there were no predisposing or risk factors for disease except for ethnicity. Compared to a study of bone and joint TB in Denmark in the 1980s, the total incidence is the same, but there has been a shift in patients from old Danes to young immigrants. The increasing number of bone and joint TB cases among immigrants is due to recent immigration of Somalian refugees, who have a high incidence of TB and a high proportion of extrapulmonary TB. The diagnosis was often delayed several months or years. This study shows that attention must be paid to this condition, particularly in young patients from an endemic immigrant population.