Severe and complicated malaria is an important cause of mortality in Plasmodium falciparum infection. We describe in this study the details of 532 cases of such syndromes admitted to hospital during an outbreak of malaria between September-December 1994. Increase in the annual rain fall, collection of water around Indra Gandhi Canal, forestation of shrubs around it and migration of labor, adaptation of Anopheles stephensi to desert climate and favorable breeding of An. culicifacies in the areas under impact of irrigation were presumptive causes of the outbreak in this region. Cerebral malaria (25.75%), hepatic involvement (11.47%), spontaneous bleeding (9.58%), hemoglobinuria (7.89%), severe anemia (5.83%), algid malaria (5.26%), ARDS (3%) and renal failure (2.07%) were the important manifestations. The overall mortality was 11.09%, which was high because of infection in the non-immune population of this area. Ignorance about the severity of this disease and lack of transportation facility was another important factor. Morality was highest in ARDS (81.25%) followed by severe anemia (70.97%), algid malaria (46.43%), renal failure (45.45%), jaundice (36.06%) and cerebral malaria (33.57%). Pregnancy was an important determinant increasing the mortality in female patients. Mortality was very high (82.35%) in those persons who presented with more than 3 syndromes together.