Colleges and state higher education agencies too often lack accurate information about the socioeconomic status (SES) of their students. This paper describes the methodology that Community College Research Center (CCRC) researchers used to estimate the SES of individual students in the Washington State community and technical college system using SES descriptors from the Census information on their geographic area of residence. Data collected by the federal government for the decennial Census provide indicators of SES for relatively small, homogenous geographic areas known as "block groups." Students' addresses were matched with Census block groups and then classified according to the average SES characteristics of their block group. The paper is organized as follows: Following an introduction, the second section describes how CCRC linked students with block groups to estimate their SES, defined in terms of household income, education, and occupation. This analysis was conducted by using data from both the 1990 and 2000 Censuses. In the third section, CCRC used cluster analysis to combine Census block groups into 15 demographically distinctive "community clusters," and then matched each student with a cluster. Doing this enabled them to classify students according to a richer set of information than just income, education, and occupation. These community clusters will be useful to the Washington State Board for Community and Technical Colleges (WSBCTC) and its member colleges in gauging their "market penetration" in various demographic sectors of the state, and in identifying particular communities where students may face barriers to college access. Given the interest of the state in ensuring access to college by students from low-income families, the fourth section shows how the community clusters break out by SES. This paper concludes with some suggestions for ways that state agencies and colleges in other states can use this methodology. (Contains 5 figures, 2 tables, and 3 endnotes.) [This publication was written with David Prince and Doug Whittaker.]