This study aims at providing a comprehensive account of the types of errors produced by Saudi EFL students enrolled in the preparatory year programe in their use of articles, based on the Surface Structure Taxonomies (SST) of errors. The study describes the types, frequency and sources of the definite and indefinite article errors in writing compositions. Data were collected from written samples of 150 students. They were given one-and-a-half hours to write on one of four different descriptive topics. Analysis of inter-lingual and intra-lingual sources of article errors revealed that the frequency of eliminating both the indefinite articles and the definite article was higher than the frequency of inserting and substituting one article with the other. The study also shows that errors of using "a" were more common than errors of using "an" and "the" in the writing texts. This result also indicates that L1 interference strongly influences the process of second language acquisition of the articles, having a negative effect on the learning process. Pedagogical practices including comparison of article use in learners' both language systems may improve learners' ability to use the articles correctly in writing and the other language skills.