Acetylcholine (ACh)-gated single channel events were studied on the TE671 human medulloblastoma clonal cell line by the use of the cell-attached patch clamp technique. Channel activity was detected (86% probability) in the presence of 0.1-2 microM ACh but not (0% probability) in the absence of agonist or in the presence of 1 microM alpha-bungarotoxin (Bgt). This effect of Bgt was reversible within 1 h. The most prominent channel type had a conductance of 50 pS. The kinetics of opening and closing of the channel were similar to that for skeletal muscle nicotinic acetylcholine receptors.