If retirement means a substantial and sustained reduction in the time spent working for pay or profit, measurement requires a definition of substantial and sufficient observations of the same individuals to determine whether a transition from working to retired status has occurred. Using the Statistics Canada Longitudinal Administrative Databank, a 20 percent sample of the individual income tax returns of all tax filers since 1980, we identify those with significant labour force attachment at ages 50-52, and follow them year by year. If retired means having no income from employment, the median age of retirement is about 63 for men, 62 for women. That is true for all cohorts. If earning up to half of one's previous employment income is deemed consistent with being retired, the median age is about 60 for both men and women. Results obtained in this way are consistent with calculations based on Labour Force Survey data.