As part of the European project TRANSAT H2020 we organize the First Tritium School at the Jožef Stefan Institute The school will be held from March 25 to March 28, 2019, in the main lecture room of the institute. Experts in the field of fusion and fission from around the world will hold lectures on different topics related to tritium such as tritium detection, management, control, retention and waste. One day will be also dedicated to radiotoxicity, ecotoxicity and dosimetry of tritium in organisms.