This retrospective study was conducted in order to determine the incidence of various complications of Plasmodium vivax malaria based on a review of case records in a tertiary care hospital in New Delhi, India. The case records of all confirmed cases of malaria over the period of one year were studied. Complete blood count, peripheral blood findings, liver and kidney functions were reviewed. There were 165 confirmed cases. Of these, 121 were due to P. vivax and 42 to P. falciparum. Two cases had mixed infection. The complications seen in the P. vivax cases were: thrombocytopenia; hepatic dysfunction; renal damage; and acute respiratory distress syndrome (ARDS). There were three deaths as a result of ARDS. This paper highlights the fact that P. vivax malaria, although considered to be a benign entity, can have a severe and complicated course, which is usually associated with P. falciparum malaria.