STUDY OBJECTIVE: To estimate the point accuracy of adult registration on the community health index (CHI) by comparing it with the electoral register (ER) and the community charge register (CCR). DESIGN: Survey of overlapping samples from three registers to ascertain whether respondents were living at the addresses given on the registers, analysed by capture-recapture methods. SETTING: Aberdeen North and South parliamentary constituencies. PARTICIPANTS: Random samples of adult registrants aged at least 18 years from the CHI (n = 1000), ER (n = 998), and CCR (n = 956). MAIN RESULTS: Estimated sensitivities (the proportions of the target population registered at the address where they live) were: CHI--84.6% (95% confidence limits 82.4%, 86.7%); ER--90.0% (87.5%, 92.5%), and CCR--87.7% (85.3%, 90.3%). Positive predictive values (the proportions of registrants who were living at their stated addresses) were: CHI--84.6% (82.2%, 87.0%); ER--94.0% (90.9%, 97.1%), and CCR--93.7% (91.7%, 95.7%). CONCLUSIONS: The CHI assessed in this study was significantly less sensitive and predictive than the corresponding ER and CCR. Capture-recapture methods are effective in assessing the accuracy of population registers.