In order to determine whether the concept ’’phoneme boundary’’ has validity independent of the particular experimental paradigm used to measure it, four procedures were used to locate phoneme boundaries on two acoustic continua: a VOT continuum, and a formant transition continuum. The procedures were a standard identification test, a version of the method of adjustment, an adaptive psychophysical procedure (PEST), and a version of the method of limits. The procedures differed in reliability, and there were substantial individual differences in the locations of the phoneme boundaries, but the correlations between boundary locations for each subject found by the different methods were quite high. Thus the ’’locus of the phoneme boundary’’ represents an internal variable which can be measured in a number of different ways. We also examined a subsidiary question. A hardware synthesizer does not produce identical waveforms given the same stimulus parameters twice. Do these different tokens produce the same perceptual responses? In the identification tests, different tokens of the various stimuli elicited different average rating responses. Thus, there are reliable (but quite small) token effects for synthetic speech stimuli which can affect phonetic perception.