Six-, 12-, and 18-month-old English-hearing infants were tested on their ability to discriminate nonword forms ending in the final stop consonants /k/ and /t/ from their counterparts with final /s/ added, resulting in final clusters /ks/ and /ts/, in a habituation-dishabituation, looking time paradigm. Infants at all 3 ages demonstrated an ability to discriminate this type of contrast, a contrast that constitutes one phonetic cue for the English morphological concepts of plural, possession, and person. These results suggest that across a significant portion of the development of infants' speech perception, this type of final contrast is discriminable. (Contains 5 footnotes, 1 table and 1 figure.)