The comparative findings on computed tomography scanning and angiography prior to and after spontaneous rupture of a craniopharyngioma cyst in a 17-year-old boy are described. Spontaneous rupture of craniopharyngioma cyst is extremely rare and we have been able to find only two such cases. The present case is the first case that was recognized by computed tomography scanning prior to and after the episode of rupture and verified histologically after operation.