On the occasion of 100 years of the birth of acad. Kiril Bratanov (1911 – 2011) The Ministry of Transport, Information Technology and Communications issued an illustrated postal envelope with his portrait and standard mark for the price of the postal service – 0.65 lv., 1615 envelopes in circulation. The envelope is with a special postal mark which includes the symbols of the reproduction – the scientific field studied in the works of acad.Bratanov and an inscription “100 years of the birth of academician Kiril Bratanov”. The validation of the postal envelope was done on March 2^nd 2011 in the Museum of the Bulgarian Postal Service. At the ceremony were present representatives of the Bulgarian Post, officials from the Ministry of Transport, Information Technology and Communications, directors and personnel of the Institute of Biology and Immunology of Reproduction, Bulgarian Academy of Sciences, philatelists, and representatives of non-governmental organizations. The Director of the direction “Communications” at the Ministry Andreana Atanasova introduced the new issue and associate professor Margarita Mollova (IBIR, BAS) delivered a short speech about the life, the activities and the merits of acad. Kiril Bratanov as a scientist and social activist.