Context:Both malaria and lymphatic filariasis (LF) are mosquito-borne diseases caused by protozoal and nematode parasites, respectively, and are serious public health problem in India. Although the vectors of the diseases are different, they can coexist in favorable conditions. Fever is the common symptom for both the diseases, but the emphasis is given for diagnosis and treatment of malaria due to its life-threatening severity, LF remained neglected. Detection and management of microfilaria are equally important. During the diagnosis of malaria, a few microfilaria were detected, which prompted us to undertake this study with following objectives.Objectives:The objective of the study was to determine the incidence of microfilaremia among the febrile patients attending for malaria diagnosis.Subjects and Methods:Thick and thin peripheral blood smears from all patients attended were examined following Giemsa staining. Different malarial indexes were analyzed.Results:Out of 8681 patients examined, 1778 were positive for Plasmodium vivax and 328 for Plasmodium falciparum with a slide positivity rate 20.48%. Twenty-six patients were positive for microfilaria of Wuchereria bancroftii among which five were coinfected with P. vivax and one with P. falciparum. Most of the microfilaria-positive patients were adult and originally from northern districts of Bihar.Conclusions:High incidence of microfilaria among febrile patients attending for malaria is alarming for urban Kolkata. Although the patients were originally from Bihar, they are staying in Kolkata for a long time, might be a source for transmission. Epidemiological study by collecting night blood samples and entomological survey is highly suggestive to explore local transmission if any.