We report the results of a retrospective analysis of the clinical charts of imported malaria cases notified during the period 1991-95 in the Lombardy region of northern Italy. We analysed 694 admissions related to 683 individuals. The proportion of immigrants increased during the observation period from 34.4% in 1991 to 59.9% in 1995 (P = 0.002). P. falciparum was the causative species in 534 cases (78. 2%), and 591 (90.1%) of 656 cases with a full travel history had travelled to Africa. Information on chemoprophylaxis was available in 604 cases: 429 (71.0%) reported no drug intake, 140 (23.2%) an incomplete, and 35 (5.8%) a complete chemoprophylactic course. The proportion of subjects who had initiated malaria chemoprophylaxis was significantly lower among immigrants (7.4%) than nonimmigrants (50.2%) (P < 0.001). Severe disease was diagnosed in 26 (4.7%) of 551 cases of falciparum malaria, with a significantly lower incidence among immigrants (1.3% vs. 9.2%; P < 0.001). Eight deaths were recorded, all among nonimmigrants, whose fatality rate was significantly higher (P = 0.02). Mefloquine treatment of cases of uncomplicated falciparum malaria was associated with a significantly shorter fever clearance time (2.8 days +/- 1.5 vs. 3.5 days +/- 1.9; P < 0.001) and mean hospital stay (5.9 days +/- 4.4 vs. 8.3 days +/- 5.1; P < 0.001) compared to quinine treatment.