MRI of a rare case of polyneuritis following brucellosis is presented. An 8-year-old boy with a history of brucellosis showed marked enlargement of the origin of the left fifth cranial nerve and contrast enhancement of the fifth cranial nerves and the Gasserian ganglion in Meckel's caves. A well-defined low-signal cystic mass showing peripheral contrast enhancement lay anteromedial to the left seventh and eighth cranial nerves. The seventh and eighth nerves showed marked enhancement. The prechiasmatic portion of the right optic nerve showed fusiform enlargement with marked contrast enhancement of the nerve and right optic tract. MRI immediately after treatment showed no enhancement of the cranial nerves. Enlargement of the origin of the left fifth cranial nerve persisted, but there was no enlargement of the optic nerve. The mass near the left seventh and eighth cranial nerves was still present with no obvious morphological change, but no longer showed peripheral enhancement.