Introduction: The diagnostic procedures of bone marrow aspiration and biopsy form the backbone of evaluation of patients admitted in haematology, medical oncology and a large proportion of patients in general medicine as well. Aims: To conduct a comparative analysis between bone marrow aspirate and bone marrow trephine biopsy, as well as to ascertain the most favorable length of trephine biopsy for detecting lymphoma infiltration. Method: A total of 2006 patients were evaluated over a period of four years. All of these patients underwent bone marrow aspirate and trephine biopsy examination. Biopsies were fixed in formalin, and then decalcified in 5 % nitric acid , processed and stained with H & E, and special stains, wherever required. Results of Aspirate and Biopsy examination were compared, correlation noted and validity parameters for aspirate were calculated. Relationship between marrow infiltration by lymphoma cells and trephine length was studied and correlation was assessed. Results: Aspirate was found to have a high sensitivity for acute leukemia (100%) and multiple myeloma (80.48%), moderate for myeloproliferative neoplasm’s (74.19%) and metastasis (58.33%) and low for Non-Hodgkin lymphoma (38.46%). Lymphoma positivity increased with trephine length, with maximum positivity (85.71%) seen in 25-28 mm group and no further gain beyond 30 mm. Conclusion: Aspirate exhibits a notable level of specificity, while its sensitivity varies depending on the specific disease being considered. With the exception of a few cases where aspirate alone is satisfactory, biopsy is necessary in the majority of situations. When evaluating lymphoma positivity, it was discovered that preprocessing trephine length of 25-28 mm, examined at multiple deeper levels, yielded optimal results.