The study was renewed in February 2000 to extend and enhance several techniques in the analyses of longitudinal data frequently encountered in epidemiological studies. The techniques include: methods for control for time-dependent confounding in epidemiological studies; developing an incidence model for benign breast disease using the Nurses' Health Study; analysis of incomplete longitudinal data from the Normative Aging Study; extending the penalized likelihood procedures for quantile regression to the repeated measures setting; and development of methods to estimate correlated ROC curves to measure the predictive accuracy of GEE regression models for longitudinal data.