Context: Delayed or inaccurate communication between hospital-based and primary care physicians at hospital discharge may negatively affect continuity of care and contribute to adverse events. Objectives: To characterize the prevalence of deficits in communication and information transfer at hospital discharge and to identify interventions to improve this process. Data Sources: MEDLINE (through November 2006), Cochrane Database of Systematic Reviews, and hand search of article bibliographies. Study Selection: Observational studies investigating communication and information transfer at hospital discharge (n = 55) and controlled studies evaluating the efficacy of interventions to improve information transfer (n = 18). Data Extraction: Data from observational studies were extracted on the availability, timeliness, content, and format of discharge communications, as well as primary care physician satisfaction. Results of interventions were summarized by their effect on timeliness, accuracy, completeness, and overall quality of the information transfer. Data Synthesis: Direct communication between hospital physicians and primary care physicians occurred infrequently (3%-20%). The availability of a discharge summary at the first postdischarge visit was low (12%-34%) and remained poor at 4 weeks (51%-77%), affecting the quality of care in approximately 25% of follow-up visits and contributing to primary care physician dissatisfaction. Discharge summaries often lacked important information such as diagnostic test results (missing from 33%-63%), treatment or hospital course (7%-22%), discharge medications (2%-40%), test results pending at discharge (65%), patient or family counseling (90%-92%), and follow-up plans (2%-43%). Several interventions, including computer-generated discharge summaries and using patients as couriers, shortened the delivery time of discharge communications. Use of standardized formats to highlight the most pertinent information improved the perceived quality of documents. Conclusions: Deficits in communication and information transfer at hospital discharge are common and may adversely affect patient care. Interventions such as computer-generated summaries and standardized formats may facilitate more timely transfer of pertinent patient information to primary care physicians and make discharge summaries more consistently available during follow-up care.