Objective: To study the clinical and hematological pattern in patients with Plasmodium Vivax infection. Methods: This multi-centre cross-sectional study was conducted from April 2010 to October 2010 simultaneously at Civil Hospital Karachi, Kulsoom Bai Valika Social Security Hospital S.I.T.E and Metro Lions Hospital Metroville Karachi. 150 patients between 5 to 14 years of age with positive malarial parasite or ICT Malaria for Plasmodium Vivax or both P Vivax and P Falciparum were included in the study. Frequencies of gender, various symptoms and signs were determined, while age and laboratory alterations (Hemoglobin, White Cell and Platelet Count) were calculated by Mean + SD. Result: Most of the patients were enrolled during July to September in rainy season. 75% patients had fever of less than 2 weeks duration. Hepatosplenomegaly was detected in 49 patients. Thrombocytopenia (Platelet less than 150 x 109/L) and anemia (Hb < 10gm/dl) were found in 91% and 73% respectively. Leucopenia (less than 4 x109/l) was present in 59 (39%) and neutropenia (ANC < 1500) was found in 22 (14.7%) patients. Conclusion: Clinical manifestations of plasmodium vivax infection ranged from asymptomatic to severe complications including cerebral malaria, acute renal failure, acute hemolytic crisis and hepatic dysfunction. Acute onset fever and hepatosplenmegaly were most common clinical manifestations found in 75% and 32.6% cases respectively. Anemia and thrombocytopenia were more frequent haematological parameters whereas leucopenia was less common in this study.