A larger number of publications on cases of. complicated vivax malaria in the world literature can be. explained by a set of diffeetit faciors'. There has been unification of the definition of complicated tertian malaria allowing ihe clinical nianagement of a patient and the reporting of complicated cases of P.vivax to be improved. The, epidemiological characteristics of complicated vivax malaria are determined by a diversity of geographical, races, variants, gentyies and phenotypes of tertian malaia due to intensive internal and external migration. Chloroquine resistance and primaquine refractoriness contribute to increased local malaria transmission due to a rise in cases of reinfection during-epidemics of vivax malaria. From an epidemiological point of view, the increasing number of complicated vivax malaria cases indicates the untimely detection and treatment of malaria patients, the low level of medical personnel training and a negative attitude of the local population towards the recommendations of national malaria programs for prevention measures. Unsolved problems can substantially retard the time to achieve malaria elimination.