Prior research has found poor communication between hospital-based and primary care physicians and has suggested that this may contribute to medical errors. This systematic review included 19 studies assessing the transfer of information at hospital discharge between hospital-based and primary care providers (PCPs), or evaluating interventions aimed at improving the timeliness and quality of discharge information. The review found that timely communication of discharge summaries was low, with 55% (median) transferred to PCPs within 48 hours and 85% (median) within 4-weeks; 8.5% of discharge summaries were never transferred. Discharge summaries nearly always contained patient demographics, admission/discharge dates and primary diagnoses, but less frequently included pending test results, diagnostic tests performed and discharge medications.