Are neonates sensitive to the different rhythmical units that are used in different spoken languages? And do they use these units to represent and discriminate multisyllabic words? In the present study, we used the High-Amplitude Sucking procedure to test whether 3-day-old French infants discriminate lists of Japanese words. The lists of words differed either in the number of syllabic units or in the number of sub-syllabic units such as morae. In Experiment 1, infants heard bisyllabic versus trisyllabic words (e.g.: iga vs. hekiga); in Experiment 2, they were presented with bimoraic versus trimoraic bisyllabic words (e.g.: iga vs. iNga). The results corroborate those obtained by Bijeljac-Babic, Bertoncini, and Mehler (1993), providing further evidence that neonates discriminate bisyllabic from trisyllabic words. In contrast, neonates do not appear to discriminate bisyllabic words that vary in number of sub-syllabic units. It is proposed that syllables are particularly salient units during the initial stage of speech processing, irrespective of which language and rhythmical structure is heard.