Legislation influences the availability of embryos for research. The law in Switzerland, and in some other European countries, is restrictive concerning medically assisted reproduction and stem cell research. Swiss law prohibits the creation of embryos for research purposes. It permits the derivation of human embryonic stem cells for research from surplus embryos but prohibits research with intact surplus embryos and embryo donation to other couples. Swiss law defines all embryos generated during a reproductive cycle and not used for reproduction as surplus embryos. The aim of this study was to evaluate the surplus embryos generated in Switzerland in 2003. A detailed questionnaire was sent to all registered IVF units in Switzerland (n = 22). 11727 embryos were generated during 2003. Of these, 93.5% were transferred into the uterus and 0.4% were cryopreserved. The remaining 6.1% (n = 711) became surplus. Of these, 2.7% were transferred intravaginally and the rest discarded due to poor quality (1.6%), development arrest (1.5%), renunciation by the couple (0.2%) or for other reasons (0.1%). The number of surplus embryos in Switzerland in 2003 was evaluated. Most surplus embryos became so during a therapeutic cycle. The restrictive legal regulation decreases the availability of human embryos for research.