An electronic percussion instrument which is capable of accurately discriminating roll performance to thereby electronically produce percussion tones closer to tones produced by a natural percussion instrument. A waveform memory 6 stores waveform data of percussion tones to be output for roll performance and waveform data of percussion tones to be output for non-roll performance. A work memory 4 stores values of parameters. A drum pad 1 has a percussion surface part 10, and a percussion pattern-detecting section detects a pattern of percussion applied to the percussion surface part 10 of the drum pad 1 and outputs a value of the parameter indicative of the detected pattern of percussion. The values of the parameter output from the percussion pattern-detecting section are sequentially stored in a buffer area of the work memory 4 in the order of output. Whenever a new value of the parameter is stored in the buffer area, a waveform data-determining section determines one of the two waveform data stored in the waveform memory 6 according to at least two values of the parameter stored before the new value of the parameter was stored and the new value of the parameter. A tone generation controller 7 reads out the determined waveform data from the waveform memory 6 and outputs a musical tone signal generated based on the read-out waveform data.