Fifteen beta-carboline derivatives, including those found in the South American hallucinogenic plant Banisteriopsis caapi, were injected IP and IVC into mice. Subsequent behavioral changes were observed and the levels of the compounds in brain tissue were determined. It was found that following IP administration, tremors and/or convulsions were induced by beta-carbolines having aliphatic alkyl groups, but not by those with carbonyl and oxo groups substituted at carbon-1 of the C ring. These effects were potentiated by the presence of a methoxy group at carbon-7 of the A ring, and their duration of actions were prolonged by 3,4-dihydro derivatives. When induced, tremors/convulsions correlated with levels of beta-carbolines in the brain. The smaller ED50 values of beta-carbolines that cause tremors/convulsions showed lower levels of beta-carbolines in brain tissue.