Longitudinal studies are examined with special reference to the Ontario Longitudinal Study of Aging (LSA). The specific aspects discussed are the representativeness of the sample, attrition rates, end-points, and associations, particularly the associations with age. It is concluded that, in comparison with other longitudinal studies, both in Canada and the U.S., the LSA represents a good source of longitudinal data and therefore lends itself to analyses which may be used to investigate factors expected to be important in understanding various aspects of the aging process.
