A longitudinal study was conducted at Southwestern College (SWC) in Chula Vista, California, to assess the impact of the matriculation process on SWC students. Three groups of students were compared: students who started "Pre-Matriculation" (in 1985); students who started during the "Phase-In" (in 1987); and students who started "Post-Matriculation" (in 1989). The study compared the enrollment patterns, academic performance, and academic experiences of these three groups during the first five semesters of their possible enrollment at SWC. Study findings, based on an examination of the transcripts of 6,381 first-time students entering during 1 of the 3 study years, included the following: (1) the gender and age make up of the three groups remained essential the same, though during the period there was a shift in ethnicity from Anglo to Hispanic and a shift toward a higher percentage of students seeking to transfer; (2) about 60% of the students enrolled for two consecutive semesters; (3) by the third semester, 46% of all entering students from each cohort were enrolled in at least one course; (4) differences in retention, and units attempted and completed were much more pronounced across age groups over the five semesters than after the first semester; and (5) there was little relationship between matriculation and first semester retention rate, number of units completed, or successful pass rates. (KP)