In hematologic malignancies, leukaemia is categorized as the unusual proliferation of the hematopoietic cells. The confirmatory diagnosis is usually made on the aspirate of the bone marrow with or without trephine biopsy by visualizing the cell morphology and the architecture of the bone marrow. Furthermore, there are additional methods that are used to further categorize the variant of leukaemia that includes flow cytometry immune phenotyping, and genetic analysis. In India also use of molecular diagnosis is increasing rapidly for the detection of leukaemia. Techniques such as FISH and PCR are very sensitive and with accurate results have gained importance for cancer diagnosis. Further with the development of next-generation sequencing, it is likely to become an even more prominent practice in cancer diagnosis. This article focuses and elaborated on the molecular diagnosis of leukaemia