A six-year retrospective review of concomitant HIV and mycobacterial infection in the Republic of Ireland is presented. A total of 42 culture proven mycobacterial infections were seen in 40 different HIV-infected patients. There were 24 infections with Mycobacterium tuberculosis (M.tb) and 18 infections with mycobacteria other than tuberculosis (MOTT), a significantly higher rate of MOTT infections in Ireland compared to a study from 1962-1981. The detection rate for all mycobacterial infections had an annual upward trend with a 4-fold increase between 1987 and 1992. In homosexuals, MOTT infections occurred more frequently than M.tb, while the reverse was true for IVDUs. Twenty per cent of the infections were seen in patients recently incarcerated. Relapse of tuberculosis occurred in 42.9% (3/7) of non-compliant patients, 2 of whom developed rifampin-resistant strains of M.tb. No patient compliant to their regimen had a relapse in disease. The overall survival of patients after diagnosis of M.tb was significantly better than those with MOTT infections, with respective one-year survival rate of 79% and 36% (log rank test, P = 0.006).