Objective: This study assessed the pattern of clinical course of hematological disorders in children diagnosed by bone marrow aspiration/biopsy in a tertiary care centre. Setting: The study was conducted at the Department of Pediatrics, Lahore General Hospital, Pakistan. Design: A retrospective descriptive study. Duration of study: Jan 2006 to Dec 2010. Methods: The clinical and laboratory data of 250 patients including complete history, physical examination, investigations and bone marrow examination reports were collected and then analyzed retrospectively. On the basis of these data, relative frequency of different hematological disorders was determined. Results: A total of 250 patients were selected during this study period where their bone marrow was sent for the investigations. Out of these cases, double deficiency anemia was the commonest diagnosis (22%) followed by aplastic anemia (13.6%), megaloblastic anemia (13.2%) and iron deficiency anemia (5.6%). For hematological malignancies, acute lymphoblastic leukemia (ALL) was observed in 27 cases (10.8%) followed by acute myeloid leukemia (AML) in 12 cases (4.8%), lymphoma in 8 cases (3.2%) and chronic myeloid leukemia (CML) in only two cases. Idiopathic thrombocytopenic purpura (ITP) was reported as frequent as 13.2% (33 cases). Conclusion: The pattern of non malignant hematological disorders in children diagnosed by bone marrow aspiration/biopsy was more common than malignant conditions. Double deficiency anemia was the commonest non malignant condition followed by aplastic anemia, idiopathic thrombocytopenic purpura and megaloblastic anemia. ALL was the most common presentation of the hematological malignancy.