Summary of Work: The purpose of this intra-agency agreement (Y02-AG-5-0282) is to support the measurement of aortic pulse wave velocity (APWV) as a measure of arterial stiffness in the NHLBI Activity Counseling Trial (ACT). This portion of the trial was designed to test the hypothesis that increases in physical activity resulting from educational interventions will reduce arterial stiffness. The setting is appropriate for this hypothesis testing because of the prospective nature of the study and the range of interventions which have been adopted. The measurements were taken at three points in time when other physiologic measures were taken. This allows assessment of intra-individual variability as well as the possibility of examining change over time in these measures in relation to the level of compliance with the physical activity intervention. The study has taken place in three geographic locations to assure adequate sample size for subgroup analysis: Memphis, TN, Dallas, TX and Palo Alto, CA. Pulse wave velocity was measured by two Doppler flow velocity probes simultaneously measuring the carotid and femoral arteries. A computer algorithm calculated average flow velocity tracings on a beat-to-beat basis. The time needed for the pressure wave to travel from the proximal to distal sampling site was calculated from the foot of the pressure wave. All examinations have been completed, and both cross-sectional and longitudinal data files have been prepared for analysis. While the numbers of individual participants with readings at all three time periods is relatively small, there are sufficient numbers of persons with a baseline and at least one follow-up reading to permit longitudinal analysis to assess the effect of the intervention on the measures of stiffness. Analysis of the baseline data has now been completed and a manuscript accepted for publication in the American Journal of Cardiology. Results show that age and HDLc cholesterol remain as significantly associated with baseline pulse wave velocity in multiple regression models adjusted for a large variety of covariates. Analysis of the longitudinal data is now underway and will examine the consistency of the baseline association over time and the effect of the exercise intervention on changes in pulse wave velocity.