From diverse parts of POLYALTHIA NITIDISSIMA, thirteen isoquinoline alkaloids have been isolated and identified. They belong to the structural types of benzylisoquinolines, aporphinoids, protoberberines and mainly bisbenzylisoquinolines. Four of these dimers, namely N,N'-dimethyllindoldhamine, isodaurisoline, 7-O-methyllindoldhamine and 7'-O-methyllindoldhamine, are new natural products.