In extensive searching of biomedical literature, especially for systematic reviews, it is common practice and usually required to search multiple databases. Depending on the specific subject it can range from 2 to more than 10 databases. The results will therefore contain many duplicates. But deduplication can be a time-consuming process and is sensitive to faults.We describe a method (the Amsterdam Efficient Deduplication (AED) method) which is efficient, highly reliable and time saving.