The inclusion of neurocognitive end points in clinical trials of patients with CNS tumors is increasing. Neurocognitive end points are used to understand what cognitive problems exist before treatment to establish a baseline by which the effect of treatment is judged, and to determine whether different treatment regimens improve neurocognitive function due to better tumor control, slow expected neurocognitive deterioration due to the tumor, or have more or less short- and long-term neurotoxicity. However, the use of neurocognitive end points in clinical trials for patients with CNS tumors is in its infancy, so that long-term outcomes are difficult to predict and the ability to determine the effects of different agents and treatment approaches is scant. Including this aspect of patient evaluation in addition to survival and time to tumor progression will yield better risk-versus-benefit assessments as well as provide a basis for improving interventions.