Building on previous studies of cross-linguistic influence (CLI) on SLA, and principled criteria for confirming its existence in L2 data, an empirical study was run on 74 Arab learners of English (ALEs). A detailed analysis was made of interlanguage stages of the simple past tense forms in 222 written texts produced by ALEs in the classroom settings. Written texts were collected from each subject at 3 stages in the experiment (after 2 weeks, 2 months and 4 months). The analysis of the non-target-like forms indicated that interlanguage stages do not appear in isolation. Quantitative and qualitative analysis in addition to descriptive analysis indicated seven interlanguage stages that ALEs may go through in the acquisition of the simple past. The stages will be presented and detailed examples will be given of the way in which the non-target-like forms were categorized.