This study describes 14 cases of relapse and recrudescence of malaria, treated between 1991 and 2003. In that period, 146 patients were hospitalized in the Clinic of the Institute in Gdynia: 20 women and 126 men. In 103 cases the disease was caused by Plasmodium falciparum, in 31 cases by Plasmodium vivax, in 5 cases by Plasmodium malariae, and in 2 cases by Plasmodium ovale. Five patients were found to have mixed infections, with either P. falciparum and P. vivax or P. falciparum and P. ovale. Relapses in patients previously treated in the country or abroad accounted for 9.6% of all the treated cases of malaria. Recrudescences and relapses were diagnosed of both the tropical malaria (6 cases), and the tertian malaria caused by P. vivax (4 cases). Moreover, in 4 patients diagnosis was made of secondary malaria due to P. vivax infection, while the primary attack was caused by invasion of P. falciparum. Also discussed was the issue of drug-resistance of plasmodia and the resulting problems with the treatment.