The enrollment patterns of residents of the Rancho Santiago Community College District (RSCCD) were evaluated by comparing data on students at Rancho Santiago College (RSC) to 1990 census information. For each city and zip code, the study analyzed ethnic distributions and participation rates. Populations over 18 years of age from zip codes and cities within the RSCCD were compared with students enrolled in fall 1991 from those zip codes and cities. Major study findings included the following: (1) Santa Ana zip codes were populated more predominantly by Hispanics (57%), and Orange zip codes were populated more by Whites (74%); (2) overall, students enrolled in RSC in fall 1991 from Santa Ana were younger, more often male, and more often Hispanic than White than the students from Orange; (3) in fall 1991, 43 out of every 1,000 adult residents of the district were attending RSC for an overall participation rate of .043; (4) participation rates for the City of Orange were generally higher (.055 overall) than those for Santa Ana (.042 overall); (5) participation rates by ethnicity were highest for Asians (.111) and Blacks (.138) and lowest for Hispanics (.033) and Whites (.041); and (6) participation rates for Hispanics were highest in zip codes farthest from the campuses. (JMC)