In an attempt to better understand the role of relationship between the use of English indefinite article and L1 transfer in L2 countability judgments by speakers of non-classifier languages, the current study investigates how Saudi EFL learners judge noun countability in English. The current study aims to find; (1) if countability judgments correlate with the learners' use of the indefinite article, given that articles in Arabic (L1) are not a determining factor of countability, (2) the extent to which context aids Arabic learners of English to make better judgments of noun countability, (3) if countability judgments correlate with noun class (concrete vs. abstract), (4) whether Arabic (L1) knowledge plays a role in the judgments of noun countability in English (L2), and (5) the extent to which proficiency correlates with better performance on countability judgments. A total of 75 Saudi learners of English, who were divided into beginner, intermediate and advanced levels, completed a Fill-in-the-Blank task (FB), an Error Correction task (EC), a countability judgments of nouns in isolation (JCI), a Countability Judgments of nouns in Context (JCC), a Translation task from L1 to L2, and a Self-report task. According to correlation tests and ANOVAs, countability judgments strongly correlate with article accuracy on both the FB and EC tasks. Context was identified as an important factor in making better countability judgments as the difference between accuracy rates of the JCC and JCI was significant in favor of the former; the subjects had a flexible notion of countability, in that it is not static rather than context dependent. The results also revealed that the subjects' overall accuracy rates for abstract and concrete nouns were very close, and no significant differences were observed except in the translation task where the accuracy rate for concrete nouns was significantly higher than abstract nouns. The semantic context of abstract and concrete nouns was found to be a relevant factor to countability judgments; the subjects performed better on the count use of concrete nouns than the mass use, while their accuracy rates were very close for the count and mass uses of abstract nouns. The results of the translation task showed that L1 had an influence on countability judgments in L2, which was evident in the fact that the accuracy rate for this task was the lowest. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]