An expression of cellular transformation in chicken embryo fibroblast infected with Rous sarcoma virus (RSV) was inhibited by 3-deazaguanine (3-DG). Re-transformation of normal rat kidney cells infected with a temperature-sensitive mutant of RSV was suppressed by 3-DG when the cells were shifted from the non-permissive temperature (38 degrees C) to the permissive temperature (33 degrees C). Removal of the inhibitor enabled the cells to revert to the transformed state. Finally, 3-DG had little or no effect on replication of RSV in the chicken embryo fibroblast cells.