Morris hepatoma 7794A was found to have its c-myc gene amplified 5- to 10-fold. The over-expression of c-myc was observed in all three hepatomas studied (Morris hepatomas 5123D, 7136A and 7794A), although in the first two instances the c-myc genes were not amplified. Over-expression or deregulation of c-myc seems to be a general phenomenon associated with hepatoma.