Mice treated with reserpine, picrotoxin or pentylenetetrazol showed convulsions on handling. These seizures closely resembled the previously described convulsions on handling in mice undergoing alcohol withdrawal reactions. The mildest form of the convulsion was tonic, in a characteristic posture, and was evoked by gently spinning the mouse by the tail. More severely affected mice showed clonic seizures when simply lifted by the tail. Reserpine-treated mice had no spontaneous seizures but convulsions could be repeatedly elicited by handling for about 24 h after a single dose. Mice treated with picrotoxin or pentylenetetrazole showed elicited convulsions at doses that were too low to cause spontaneous seizures or at times when the overt convulsant action had ceased. The number of mice showing elicited convulsions was dose-related. Strychnine treatment caused convulsions on handling only at near-lethal doses and then in only a few mice. Convulsions on handling may be useful as a simple empirical sign of CNS hyperactivity in mice.