In United States, person is diagnosed with blood cancer in every 3 minutes. In 2015, there were 1.665.540 total cancer cases and 9.4% of them lymphoma and leukemia . In 2015, there were 95 cases of lymphoma in Mongolia when compared 4 times increase to 2015 from 2010 . Bone marrow examination is an established diagnostic modality in the evaluation of various hematological disorders. BM examination can serve to establish or confirm a primary diagnosis of lymphoma or to determine the extent of disease dissemination for staging purposes. Biopsy is essential for diagnosis in a dry tap or blood tap which occurs when the marrow is fibrotic or densely cellular. Only a biopsy allows a complete assessment of marrow architecture and pattern of distribution of any abnormal infiltrates. In 2015.01-2016.01 fifty five bone marrow biopsies were retrieved from the files of the National First Clinical Hospital-Department of Hematology. These all statistical analysis was performed using by SPSS 17. Bone marrow processing and staining: The hematologist is instructed to place the freshly obtained BMTB specimens directly into buffer substance fixative and transport it immediately to the histopathology department, on the same day as the procedure.The next morning (after 20–24 h), the solution is decanted (with a strainer) and the biopsy specimen is washed in distilled water for 30 min. The biopsy specimens are left to decalcify for about 6 h before being processed and embedded in paraffin wax, with procedures similar as for other specimens.Sections, 1-mm thick (microtome set for 1 mm sections), are cut from the paraffin-wax blocks with the routine rotary microtomes in the laboratoryA total of 55 cases were reviewed from December 2014 to November 2015. The age of the subjects ranged from twenty two years to seventy eigth years with a male predominance (1.7:1). Data of 55 trephine biopsies were reviewed. The percentage of trephine biopsies in different length ranges was calculated. Twenty two biopsieswere of recommended length, i.e., ≥1.5 Cm while remaining 33 were less than the recommended length. The rate of positivity for diagnosis was 95.4% in group-1, 94.1% in group-2, 63.6% in group-3 and 40% in group-4 In all cases in our study 73% (n=40) were satisfactory and 27%(n=15) unsatisfactory slides .Our study showed that 40% trephan biopsies were of revommended length i.e >=1.5cm with 95.4% positive of diagnosis. However biopsies measuring 1-1.4 cm also had comparable result 94.1% .