As an unusual complication of bromocriptine treatment for prolactinoma, CSF rhinorrhea has been reported in the relevant literature. The authors, on the contrary, experienced cessation of CSF rhinorrhea during bromocriptine treatment. A 37-year-old man with invasive prolactinoma underwent a frontal craniotomy for removal of pituitary adenoma on February 2, 1978. Postoperative CT showed residual adenoma within the sella and the sphenoid sinus. Postoperative irradiation was started on February 27 and given in a total dose of 5,000 rad. On March 30, 1979, the patient noticed clear fluid dropping out of his nostrils, the fluid contained glucose and CSF rhinorrhea was suspected. The CSF rhinorrhea was considered due to the regrowth of adenoma in the paranasal sinuses. On June 27, 1979, the patient developed headache together with fever and CSF rhinorrhea. On examination, the patient was drowsy and showed marked nucheal rigidity. Under the diagnosis of meningitis caused by CSF rhinorrhea antiseptic chemotherapy was started. Hypocycloidal tomogram showed extensive destruction of the sella and a soft density mass in the sphenoid and the ethmoid sinuses. CT also showed intrasphenoidal and lateral extension of the adenoma. To repair of the CSF leak, transsphenoidal surgery was performed on August 2, 1979 when the patient was in favorable condition. The sphenoid sinus was full of adenoma and it was removed, however, the exact location of the CSF leak could not be identified. The sphenoid sinus was packed with muscle tissue. Bromocriptine treatment was postoperatively started with 5 mg per day on August 25, 1979. The patient sustained CSF rhinorrhea which was decreased by lumbar drainage.(ABSTRACT TRUNCATED AT 250 WORDS)