The comparative analysis of the cases of imported malaria in Lombardy and in Italy during 1976-1980, shows that the prevalent factors of risk are, in both, the male sex, the young age, the stay in endemic areas of tropical Africa where P. falciparum is greatly prevalent. The only very significant difference is represented by the prevalence of touristic motivation of the stay among the cases of Lombardy. The efficacy of prophylaxis against these factors of risk allowed to note, in the two last years considered (1979-1980), a sharp reduction of the annual number of cases in opposition to the trend of European cases of malaria.