Introduction: Within the last five years there has been a new interest in categorical-like perception of nonspeech signals. New investigations argued that categorical perception was questionable for both speech and nonspeech continua.One of the criteria of categorical perception says that subjects are able to discriminate only sounds that are identified as belonging to different categories.To examine if this criterion holds it should be known how large the differences in onset values of acoustic stimuli have to be in order to be perceptually different.Yet,surprisingly little is known about the difference limens /DLs/ of the rise time.Van Reuven and van den Broecke /1979/ established DLs for rise time of 1000 Hz sine waves as well as white

noise bursts by means of an adjustment method. The Weber fraction was about 25%. Similar results were obtained by Kewley - Port and Pisoni /1984/ in the adaptive tracking procedure for 300 Hz sawtooth waves.In the present experiment new DL values were obtained for sine waves by a constant stimulus method with multiple comparison in a single trial.