BACKGROUND: Communication and coordination with primary care physicians (PCPs) is recommended to ensure safe care transitions for hospitalized older patients. Understanding patient experiences of problems after discharge can help clinical teams design more patient-centered care transitions. OBJECTIVE: To report older patients' experiences with problems after hospital discharge and investigate whether PCPs were aware of their hospitalization. DESIGN: Prospective mixed methods study. SETTING: Single academic medical center. PATIENTS: Hospitalized patients and PCPs. MEASUREMENTS: Telephone interviews of frail, older general medical patients conducted 2 weeks after discharge to elicit patient problems after discharge, such as: (1) obtaining medications, or follow-up appointments; and (2) perceptions of hospital physician communication with their PCP. For each patient interviewed, their PCP was faxed a survey 2 weeks after discharge to assess awareness of hospitalization. RESULTS: Forty-two percent (27) of patients reported 42 different post-discharge problems. The most frequently reported problems were difficulty with follow-up appointments or tests (12). Other reported problems included readmission and return to the Emergency Department (10), problems with medications (8), not-prepared for discharge (8), and hospital complications or questions (4). Thirty percent of PCPs were unaware of patient hospitalization. Patients were twice as likely to report a problem if their PCP was unaware of the hospitalization (31% PCP aware, vs. 67% PCP not aware; P < 0.05). CONCLUSION: This study suggests that many frail, older patients reported problems after discharge and were twice as likely to do so when the patient's PCP was not aware of the hospitalization. Systematic interventions to improve communication with PCPs during patient hospitalization are needed.