Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder as a resultof neoplastic transformation of the primitive hemopoetic cells. It is well known thatthe Philadelphia chormosome (ph) is a specific abnormality found in 90% of CMLpatients. It has been reported that interferon has better effect on disease control andprognosis. Cytogenetic analysis of ph chromosome plays very important role in theprognosis and monitoring of therapy. In this present study 35 diagnosed patients ofCML were considered, which included untreated patients of various age groups (2-62yrs). The cases were refered from haematology clinic of All India Institute of MedicalSciences (AIIMS). Out of 35 patients only 13 patients were available after six monthof therapy for follow-up cytogenetic analysis. Out of 13 patient, 2 were ph negative, 8were 100% ph positive and 3 were ph positive mosaic before therapy. Of the 3 mosaicpatients, 2 remained unchanged after therapy and one patient became 100% phnegative. Though in general significant reduction in ph% by interferon therapy wasseen but minority patients showed complete cytogenetic remissionKey Words: Chronic myeloid leukemia, chemotherapy, Philadelphia chromosome.