We conducted a retrospective survey of nocardiosis in 9 city hospitals in northern Italy from 1982 to 1992. The medical records of 30 patients with documented nocardiosis were reviewed. Microbiological data included morphology, biochemical characteristics, serology and in vitro susceptibility testing. The 29 isolates (1 case was diagnosed on the basis of serological results) were Nocardia asteroides (n = 25) and Nocardia farcinica (n = 4). Predisposing factors including immunosuppression for organ transplant rejection prophylaxis, lung disease (silicotuberculosis and pulmonary fibrosis), solid tumours and hematological malignancies, and AIDS. Three patients had no identified risk factors. 20 cases of pulmonary nocardiosis were observed. Sites of infection in patients without previous pulmonary involvement were: brain abscesses, soft tissues, pericardium, blood, and cerebrospinal fluid. Most strains tested were susceptible to amikacin and imipenem. Resistance to several antimicrobial agents was found, particularly erythromycin, fosfomycin, pefloxacin, sulphonamides and trimethoprim. Antimicrobial chemotherapy included sulphonamides, amikacin, ceftriaxone, imipenem and minocycline. 21 patients survived, although 2 relapsed transiently. Nocardiosis appears to be more common than generally realised by physicians in northern Italy. The local species distribution and disease spectrum are similar to those described elsewhere. Nocardiosis should be part of the differential diagnosis in patients with pulmonary infiltrates or brain abscess, particularly those with predisposing factors.