OBJECTIVES: Patients under hemodialysis (HD) may have many medication-related problems (MRPs) due to their medical complexity. The study objective was to identify MRPs experienced by inpatients under HD upon admission in Wang-Fang hospital in Taiwan. METHODS: Patients on either regular or irregular hemodialysis from 24th October to 11thNovember in 2011 were included in this study. Patients who did not use any drugs were excluded. Demographic and types of MRPs were assessed by descriptive statistics. RESULTS: A total of 81 patients were evaluated, and 67 MRPs were identified. Each patient used 11 drugs on average. Patients using over 12 drugs were at higher risk of occurring MRPs. Among the 67 MRPs, the most common type of MRP was drug interaction (50.7%), followed by overdose (37.3%). Pharmacists intervened 17.91% of the MRPs and also kept monitoring 58.2% of the MRPs. Physicians accepted 91.67% of the pharmacy interventions. Patients under regular (n=67) or irregular HD (n=14) were also compared in our study. Different types of MRPs were shown between the two groups. Drug interaction occurred more often in patients on regular HD (n=32, 47.8%), while overdose was more commonly discovered in irregular HD group (n=7, 50%). CONCLUSIONS: MRPs exist commonly in HD patients. The study showed that patients using 12 or more drugs were at higher risk of occurring MRPs. Patients under regular or irregular HD may have different patterns of MRPs. Pharmacists should be more careful when evaluating these patients’ medications.