The present study examines Saudi ESL learner perception of three syllable-final English nasal contrasts:/n/-/m/,/m/-/ /,and/n/-/ /.It was based primarily on two models,the Perceptual Assimilation Model(PAM)and the Speech Learning Model(SLM),in order to determine how Saudi ESL learners categorized nasal segments in their L2, English.Other models,including the Markedness Differential Hypothesis(MDH), contributed in finding the most difficult contrast.The participants,consisting of 24 Saudis studying in the US,were asked to distinguish between 40 English monosyllabic words grouped into minimal pairs.Regardless of their length of exposure,participants had greater difficulty in categorizing/n/and/ /as separate phonemes, dealing with these sounds as a Single Category(SC).The/n/-/m/contrast had the fewest errors among participants with more exposure in the US,who were able to distinguish between the word pairs in this contrast, while those with less exposure had more difficulty in distinguishing/n/from/m/.This fact shows that the participants were able to categorize the/n/and/m/ as a Two Category(TC).The contrast/m/-/ /had a number of errors somewhat similar to that found with the/n/-/m/.