OBJECTIVE: To find out clinical features, diagnostic techniques and management outcome of patients having dual dengue and malaria infection. STUDY DESIGN: A case series. PLACE AND DURATION OF STUDY: Medical Unit-III, Ward- 7, Jinnah Postgraduate Medical Centre, Karachi, from September 2007 to January 2008. METHODOLOGY: Patients presented with fever of less than or equal to 10 days duration, severe body aches, rash and bleeding manifestations were included. Patients with obvious features of other diseases like typhoid, hereditary bleeding diathesis and hematological malignancies and only malarial parasite positive with high grade intermittent fever without rash and myalgia were excluded from the study. Diagnosis of dengue and malaria was based on history, clinical features, laboratory parameters and malarial parasite test by thin and thick films. Serological evaluation was done by dengue IgM and IgG by ELISA test kit. Patients were divided into three groups. Group A was dengue IgM positive plus MP positive, group B was dengue IgM positive and MP negative and group C was dengue IgM negative and MP negative and were clinically suspected dengue and malaria. The clinical manifestations and laboratory parameters of dual dengue and malaria positive patients were compared with malaria and dengue negative patients. RESULTS: One hundred and fourteen patients were seen during the study period. Antibody titer (IgM) tested in all patients was found positive in 78 patients (69.64%). Among those 78 patients, 26 (23.21%) were concomitantly positive for malarial parasite (Group A). Plasmodium vivax was positive in 25 patients and falciparum in one patient. Fifty-two patients (46.42%) were dengue IgM positive and MP negative (Group B). Thirty four (30.35%) patients were MP and dengue IgM negative (Group C) but were strongly suspected for DHF and malaria on clinical and hematological basis. The hemoglobin of 34.61% of patients of group A, 5.76% of group B and 14.7% of group C were low, hematocrit level was also low in group A (92.3%), group B (15.38%) and group C (70.58%) patients. The platelet count was markedly low in 84.61% of patients of group A, 57.69% of group B and 94.11% of group C. Leukopenia was found in 34.61% of patients of group A, 78.84% in group B and 29.411% in group C. The liver function tests were deranged in all groups. CONCLUSION: The frequency of dual dengue and malaria infection was 23.21%. The serology of the dengue and malaria showed negative results in 30.35%. The diagnosis of dual infections could be made on the basis of history, clinical examination supported by hematological results. It is recommended that all the patients suspected for dual infections should be treated concomitantly for dengue and malaria in malaria endemic areas.