The anatomy of a follow-up.

This article describes the methods that were used to maximize subject retention in an 8-12 year follow-up study of 454 men. Guidelines and suggestions are given regarding follow-up structure, strategies to relocate lost subjects, and efforts to maintain contact and ensure subject cooperation. Through these methods all 454 subjects have been located, and at the present time an estimated 98% or greater will be completely evaluated at follow-up. Hopefully these suggestions will be helpful to researchers and clinicians interested in longitudinal studies.