This study concentrates on utilizing registries and assessing their quality for population-based research. A method of successive comparisons is used to develop and update a summary record of coverage (length of time on the registry) and mortality for each individual in the Manitoba Health Services Commission data base. Various ways to ascertain the accuracy of the summary records are discussed. These techniques are validated by efforts to follow over an 8-year period 4,794 individuals interviewed in 1971 as part of ongoing research on the Manitoba elderly. Ninety-seven percent of the total elderly sample (and 99% of those successfully matched with interviewees) were traced over 8 years. Deaths recorded on hospital claims but not on the master registry and possible unrecorded out-of-hospital deaths are outstanding problems with the Manitoba data base. Further checks against 1970-1977 vital statistics information in the Canadian Mortality Data Base will be made.