A study examined the stages of acquisition of Spanish definite articles by two groups of English-speaking learners enrolled in their first semester of Spanish. The approach taken was to analyze writing samples produced by the groups at different times during the semester, to obtain the basis for a pseudo-longitudinal analysis of article usage. The main goal was to expose variability in the students' interlanguage systems and to propose early developmental stages in the acquisition of articles. Results support studies postulating a natural order of acquisition, and showed a relatively significant incidence of first-language (L1) transfer consistent with the weak form of the Contrastive Analysis Hypothesis. L1 interference seems to be only one of many factors in acquisition. Existing theories on natural order of acquisition and interlanguage provide a framework for analyzing the results. Interaction of several factors (simplification, communicative value, frequency of input, first language transfer) was useful in accounting or some of the stages of acquisition suggested by these results. Contains 18 references. (MSE)