Malaria is most commonly transmitted by mosquito bite, but it can also be transmitted by transfusion, organ transplantation, and from mother to child. Malaria is a dangerous and lethal disease and represents a public law problem in underdeveloped tropical and soutopian countries. The disease usually occurs in tropical regions, caused by a parasite from genus plasmodium. The disease has similar flu-like symptoms, and occurs one week after the mosquito bite. Malaria symptoms include fever, jaundice, increased liver, headache, chills and anemia. There is no vaccine for malaria now, but there are also prophylactic drugs that can prevent the onset of the disease-chemoprophylaxis. Taking into account the chemoprophylaxis, consideration should be given to possible resistance to malaria. Preventive use of repellents, long sleeve clothing and sleeping with a mesh, treated with insecticides, around the bed. It is advised to avoid staying in the open at the time of the highest mosquito activity. The largest number of mosquitoes is in dawn and dusk. Every year, a number of malaria cases are imported in Croatia, and a certain percentage applies to seafarers. This number is decreasing in time, which is probably caused by the end of the ship's stopping or anchorage, which technically is disabling malaria infection.