&NA;Patients with craniopharyngiomas who demonstrate cyst enlargement after surgery and radiation are often presumed to be treatment failures. Therapeutic approaches in various centers include repetitive cyst aspirations, surgical reexcision, and instillation of cytotoxic agents such as methotrexate,32P, or198Au. Each intervention has associated severe or even lethal side effects. Not all patients with craniopharyngioma who have cystic enlargement after primary therapy require an intervention, as demonstrated by 4 patients recently managed in the University of Rochester Medical Center. Since 1978, when computed tomography was routinely in use, we have managed 11 patients with craniopharyngiomas who were treated with surgery followed by radiation therapy. Three of these patients demonstrated post‐irradiation enlargement of the residual cystic component followed by a decrease in size without surgical intervention. An additional patient showed cystic growth followed by stabilization of size. It is noteworthy that the cyst enlarged within the first 5 months after radiation therapy in the 3 patients who subsequently demonstrated a diminution in the size of their cysts. This suggests that the mechanism for cyst formation remained intact and subsequently abated because of a radiation‐induced lesion. We conclude that after treatment with surgery and radiation therapy, the cystic component of craniopharyngiomas may increase and, without intervention, subsequently decrease in size. Thus, in the asymptomatic patient who demonstrates cystic growth soon after primary therapy, close observation alone may be warranted. (Neurosurgery24:53‐59, 1989)