A clinical protocol was designed that used the dose volume histogram (DVH) of the normal liver to determine the dose of radiation to be delivered to patients with intrahepatic malignancies. The dose given to the tumor depended on the volume of normal liver that could be excluded from the boost field: 45 Gy if more than 50% of the normal liver could be excluded and 60 Gy if more than 75% of the normal liver could be excluded. Thus, dose prescription depended on the ability to perform, on a routine basis, three-dimensional (3-D) treatment planning with dose volume histogram generation. A total of 36 patients have been entered onto this study. Twenty-one of 25 patients (84%) with disease that could be delineated on CT scan were eligible for boost treatment. Successive planning attempts often produced plans which qualified for boost therapy when the initial estimate had been that boost treatment would not be possible. Patients with large tumors were sometimes able to receive boost treatment, demonstrating that individualized planning was required. These results show that intrahepatic tumors can be safely treated with high doses of radiation when dose prescription is guided by the dose volume histogram of the normal liver. Furthermore, this approach strongly promotes an active role in treatment planning, since creative planning often permitted the delivery of higher doses to the tumor.