Propagation of in vitro transformed OK10 QDP 9c cells, cloned in soft agar, results in selective amplification of the OK10 pro-viral genome to yield a 12-fold increase in v-myc oncogene expression. In addition, increased v-myc oncogene dosage correlates with an increase of the proliferative potential of already transformed cells and relieves dependence on high serum concentrations for optimal cell growth. The increased rate of cell proliferation is reflected by a much more rapid progression through all parts of the cell cycle. These results suggest that the attainment of transformed status on one hand and progressive increase in growth factor independence for optimal cell proliferation on the other hand, may be initiated by different myc oncogene dosages within the OK10 QDP 9c cell clone.