Investigation of the neuropsychological sequelae of brain tumors is extremely complex largely because the neurobehavioral consequences of brain tumors depend upon complex interactions among disease and treatment variables as well as patient characteristics. To illustrate some of these complexities, we present case studies of two patients in whom the behavioral outcome was not easily predictable on the basis of our current understanding of brain-behavior relationships in tumor patients. The case studies do illustrate how neuropsychological evaluation aids in identifying cognitive deficits which have implications for subsequent quality of life. Recommendations for future experiments and statistical analyses of neurobehavioral data of this population are given.