Intracranial fat-containing congenital tumors are characterized by negative absorption values on CT. We hereby report a case of an epidermoid cyst with subarachnoid free fats diagnosed preoperatively by CT. A 21-year-old female was admitted to our hospital because of continuous mild headache and nausea. At the time of admission, the results of her physical and neurological examinations were normal. CT, however, demonstrated multiple subarachnoid low-density spots and a suprasellar low-density area with high-density spots. In addition, there were negative absorption values (-12 -- -77), suggesting free fats. A spontaneously ruptured epidermoid or dermoid cyst was diagnosed on the basis of these findings. At surgery, a suprasellar tumor containing a yellowish, cheese-like material was confirmed. The patient made an uneventful recovery and was discharged 14 days after surgery. There have been several published reports of CT appearances of intracranial fat-containing tumors. However, spontaneously ruptured cases diagnosed by CT are rare. CT was found to be useful for the diagnosis of spontaneously ruptured cases of fat-containing tumors.