The spontaneous excitatory junctional currents (e. j. c.'s) were recorded intracellulary using voltage clamp technique in experiments performed on the isolated cutaneo-muscle bag of larvae, early pupae stadium and adult fly Drosophila melanogaster. The fast miniature e. j. c.'s with mean amplitude 0.41 nA, rise time 1.60 ms and half-decay time 3.11 ms were most frequently observed. Besides these, slow miniature (half--decay time 7--20 ms) and fast giant (amplitude 12--15 nA) were sometimes present. It was found that the time course of fast e. j. c.'s is prolonged with hyperpolarisation and with the decrease in temperature. Some drugs which effectively modify the time course of end-plate currents at the cholinergic junctions (atropine, scopolamine, lidocaine, serotonin, QX-222 and ethanol) were tested. Except for ethanol, none of these drugs when added to the muscle bath affected either the amplitude or the time course of e. j. c.'s. The properties of e. j. c.'s in different neuro-muscular junctions of vertebrates and insects are discussed.