A method for repeated sampling of cerebrospinal fluid (CSF) from freely moving rabbits was developed. Levels of guanidino compounds were estimated in the CSF of rabbits with pentylenetetetrazol (PTZ)-induced convulsions by high performance liquid chromatography. A catheter was implanted via the skull into the cisterna magna and was fixed by screws. One week after the operation, 100μl of CSF was collected with a microsyringe. PTZ solution (3.3 %) was injected intraveneously, and CSF was collected simultaneously until clonic-tonic convulsions appeared. Clonic-tonic convulsions continued for about 20 seconds. After that, no convulsion was induced for one hour after the injection. CSF was also collected 20 min and 60 min after the injection. For the control, CSF was collected 5 min before PTZ injection. Guanidinoacetic acid, creatinine and arginine were found in 100μl of rabbit CSF. Levels of guanidinoacetic acid and creatinine increased and then recovered to the control level 2 hours after convulsions. Arginine started to decrease 2 hours after convulsions and continued to decrease gradually untill 2 days after convulsions. The levels recovered to the control level 4 days after convulsions.