The overarching goal of the Center for Research in Chronic Disorders Cognitive Core over the past six years has been to facilitate the measurement of cognitive function in chronic illness research. CRCD researchers, to date, have demonstrated that cognitive problems are significant correlates of chronic medical disorders. We have shown that cognition does affect self-management of treatment regimens and that non-adherence affects functional outcomes. We have also found that traditional neuropsychological batteries are often too burdensome for medical patients and clinical researchers and that ecologically valid measures, which might better predict adherence in "real world" situations, are few and lack specificity and reliability in predicting treatment adherence. An emerging interest among researchers in chronic disorders is the trajectory of cognitive function over the course of disease progression and treatment. Another emerging interest is in the impact of cognitive (and psychological) maturity on adolescents' receptivity to interventions and adherence to treatment regimens. Thusly, in this renewal application, we will focus more specifically on measuring cognitive and psychological function as they impact on treatment adherence. Specifically, our goals are to: 1) Continue to encourage and support measurement of cognitive and psychological function, with specifically tailored test batteries, in all CRCD research projects. We will target adolescent as well as adult populations. 2) Examine the impact of cognitive function in a wider variety of treatment regimens (e.g. multiple daily medications, lifestyle changes) and with an increased focus on change in cognitive function with disease progression and treatment. 3) Utilize published, validated condensed neuropsychological test batteries, when appropriate, to decrease patient and researcher burden while yielding meaningful and valid data on cognitive function in the chronic disorder population. 4) Design and pilot more ecologically sound measures of cognitive function, specifically as it may impact on treatment adherence. We present, in this application, the background and significance information to support these goals and the methodology we propose using to achieve them.