['Automated home monitoring systems have been used to coordinate care to improve patient outcomes and reduce rehospitalizations, but with little formal study of efficacy. The Geisinger Monitoring Program (GMP) interactive voice response protocol is a post-hospital discharge telemonitoring system used as an adjunct to existing case management in a primary care Medicare population to reduce emergency department visits and hospital readmissions.', 'To determine if use of GMP reduced 30-day hospital readmission rates among case-managed patients.', 'A pre-post parallel quasi-experimental study.', 'A total of 875 Medicare patients who were enrolled in the combined case-management and GMP program were compared with 2420 matched control patients who were only case managed. Claims data were used to document an acute care admission followed by a readmission within 30 days in the preintervention and postintervention periods (ie, before and during 2009). Regression modeling was used to estimate the within-patient effect of the intervention on readmission rates.', 'The use of GMP with case management was associated with a 44% reduction in 30-day readmissions in the study cohort (95% confidence interval, 23%-60%, P=0.0004), when using the control group to control for secular trends. Similar estimates were obtained when using different propensity score adjustment methods or different approaches to handling dropout observations.'] Does postdischarge monitoring using interactive voice response system reduce 30-day readmission rates in a case-managed Medicare population?