Medication safety is a global issue, but knowledge about medication safety in low- and middle-income countries is limited. Understanding the extent and nature of the problem may contribute to develop tailored strategies for improvement. This dissertation addresses medication safety in South-East Asia, focusing on Vietnam in particular. First, a systematic literature review showed a sub-optimal quality use of medicines and insufficient attention to non-communicable diseases in the region, including in Vietnam. Secondly, an observational study in two large Vietnamese hospitals found that about one-third of all medications prepared and/or administered had at least one potentially clinically relevant error. These were in particularly intravenous medications and high-alert medications as insulin. Thirdly, a clinical pharmacist led educational intervention was effective in reducing clinically relevant intravenous medication errors, especially preparation errors, but error rates remained high. Finally, Vietnamese nurses were quite positive in their perception of safety culture, but only few recognized stress as a factor which could affect their performance. Overall, there was no correlation between the safety culture on a ward and the prevalence of medication errors, but nurses of wards with higher error rates found it more difficult to discuss errors. The results of this thesis provided additional evidence that clinical pharmacists are important in ensuring medication safety, also in resource-restricted countries such as Vietnam. They should take the lead of a multidisciplinary team to develop tailor-made interventions endorsed by hospital managers.