American listeners' perception of Japanese contrasts of vowel length (e.g., kiro vs. kiiro), consonant length (e.g., kite vs. kitte) and syllable number/length (e.g., kjoo vs. kijoo) was examined. Stimuli consisted of sentence-length utterances produced by a native Japanese talker; five minimal pairs of each contrast type were included. Questions were: a) can American listeners with no Japanese experience discriminate these contrasts, b) are there differences in relative difficulty of the three contrast types, and c) do instructions and other task variables affect performance accuracy? A categorial AXB discrimination task was used in two studies: Study 1 tested the three contrast types presented in separate blocks with detailed instructions about what to listen for; Study 2 tested the contrast types presented randomly intermixed with no specific instructions about the nature of the contrasts. Results indicated that naive American listeners could discriminate all three contrast types well above chance, and that there were no significant overall differences in relative difficulty across contrast types. Performance was significantly poorer in Study 2 where listeners' attention had not been directed to the nature of the contrasts. In both studies, there was significant and large variability in accuracy across different minimal pairs of each contrast type. (Contains 3 notes, 3 tables, and 2 figures.)