The acquisition of the English article system by speakers of article-less first languages (L1s) has been the subject of considerable research. Much of that research focuses on the extent to which second language (L2) learners interpret articles as markers of definiteness or specificity, and make use of semantic context to determine article choice (Ion in, Ko, & Wexler, 2004; Trenkic, 2008 among many others). The present thesis focuses on the role that noun type (count - mass - dual) plays as one of several factors determining the use of English articles by L2 learners whose Ll is Japanese (a language that lacks articles). Three experiments and a corpus-based frequency study are reported. The first experiment, a lexical decision task undertaken in Japanese with predominantly monolingual speakers of Japanese, aimed to determine how nouns are organised in the Japanese mental lexicon. From the findings it is argued that Japanese nouns are not specified for the mass-count distinction, although noun classifiers are. In the second experiment, a lexical decision task undertaken in English with Japanese L2 learners, it is shown that their English mental lexicons are organised in a similar way to native speakers. It is argued that this is the result of Japanese speakers using the mass-count distinction encoded by classifiers in the Ll to categorize nouns in the L2. The third experiment - a forced-choice article elicitation task - shows that the mass-count distinction is one of a number of factors that determine article choice, along with definiteness, specificity and plural marking. The weight given to each of these factors can vary from individual to individual. A final, corpus-based study of the distribution of article-NP combinations in native English usage (established through a search of the British National Corpus) suggests that the frequency of such combinations may also be a factor in determining article use by Japanese L2 speakers. It is concluded that the use of English articles by L2 speakers from an article-less L1 like Japanese is intricate, but not random, and can be explained by combinations of factors that are theoretically motivated.