To evaluate the impact of large scale population screening for elevated total cholesterol, a city-wide event was scheduled in Indianapolis during nine days in February 1987. Altogether, 29,954 individuals were screened, and more than 32% were found to be at moderate or high risk using the classification recommended by the National Institutes of Health at the time of the screening for heart disease on the basis of their total plasma cholesterol concentrations. Although larger numbers of females and whites volunteered to be screened, the screened population represented a broad range of age and education levels. Results of a followup questionnaire returned by 18% of those at moderate of high risk revealed that after receipt of an elevated cholesterol result, 67% of the respondents scheduled a physician visit. The majority of those not doing so (53%) contacted their physician for other reasons or by telephone. Results of the followup indicate that screened subjects responded appropriately to the results received. The results of this project indicate that mass screening is only one tool to successfully identify individuals at risk. Given the biases present in the screened population, other strategies should be used to identify at-risk members of population groups unlikely to participate in similar screening events.