BACKGROUND: Data on the number of individuals eligible for screening, and rates of screening, are necessary to assess national colorectal cancer screening efforts. Such data are sparse for safety-net health systems. METHODS: A retrospective cohort study of individuals ages 50 to 75 served by a safety-net health system in Tarrant County, TX was conducted to determine (a) the size of the potential screen-eligible population ages 50 to 75, (b) the rate of screening over 5 years among individuals ages 54 to 75, and (c) the potential predictors of screening, including sex, race/ethnicity, insurance status, frequency of outpatient visits, and socioeconomic status. RESULTS: Of 28,708 potential screen-eligible individuals, 20,416 were ages 54 to 75 and analyzed for screening; 22.0% were screened within the preceding 5 years. Female gender, Hispanic ethnicity, ages 65 to 75, insurance status, and two or more outpatient visits were independently associated with screening. Access to care was an important factor: adjusted odds ratio, 2.57 (95% confidence interval, 2.23-2.98) for any insurance; adjusted odds ratio, 3.53 (95% confidence interval, 3.15-3.97) for two or more outpatient visits. CONCLUSIONS: The screen-eligible population served by our safety-net health system was large, and the projected deficit in screen rates was substantial. Access to care was the dominant predictor of screening participation. If our results are replicable in similar health systems, the data suggest that screening guidelines and policy efforts must take into account the feasibility of proposed interventions. Strong advocacy for more resources for colorectal cancer screening interventions (including research into the best manner to provide screening for large populations) is needed.