BACKGROUND Patients' lack of knowledge about their discharge medication can endanger patients' safety after their hospital stay. This is especially the case with regard to medications that were newly prescribed during the hospital stay and are intended to be used after discharge or medications with an increased risk for adverse drug reactions (high-risk drugs). The aim of this study was to analyse the patients' level of knowledge about their discharge medication and to identify influence factors. METHODS In a bicentric survey patients were interviewed prior to their discharge from an acute and a geriatric rehabilitation hospital. They were asked about their discharge medication in a structured interview. Influence factors were statistically analysed by Tobit regression. RESULTS In total, 179 patients were interviewed. On average, patients named 48% of their discharge medication correctly (95% CI: 46-50%). Influence factors for knowledge deficits were the lack of a medication plan, an older age, the hospitalization in a rehabilitation hospital and a long hospitalization. 81% of the patients had at least one drug in their discharge medication, which was newly prescribed during the hospital stay. 11% of those drugs were named correctly, the potency was named correctly in 6%, the indication in 8%. For almost two-thirds of the patients at least one high-risk drug was recommended in the discharge letter, among them most frequently oral anticoagulants and opioid analgesics. 38% of these high-risk drugs were named correctly. CONCLUSIONS Our results demonstrate an urgent need to train patients about their discharge medication, especially if medications are included that were newly prescribed during the hospital stay and recommended for further use after discharge or medications with an increased risk of adverse drug reactions. Particularly older patients and patients of a rehabilitation hospital after long hospitalization should be intensively counselled and obtain a medication plan upon discharge.