SUMMARY The International Conference on the Molecular Biology and Pathogenesis of the Clostridia (Clostpath) has been the leading venue to bring together scientists and clinicians at the forefront of research on the molecular biology of clostridia and their role in health and disease. In keeping with this tradition, Clostpath 11 will cover all fundamental, translational and clinical aspects of clostridial-dependent pathogenesis, including virulence gene regulation, structure and mode of action of virulence factors, host-pathogen interactions, development of new genetic tools as well as epidemiology, diagnosis, treatment and prevention of clostridial-caused diseases. The meeting will take place August 18-22, 2019 in Leiden, the Netherlands. The program for Clostpath 11 consists of a Pre-Clostpath Young Scientist Meeting (Aug 18, 2019) and the conference itself (August 19-22, 2019). At Clostpath conferences, there are traditionally 9 sessions, with 12-20 invited speakers ? all plenary (no parallel sessions). Approximately 25 additional oral presentations will be selected from submitted abstracts. The Organizing Committee, the International Scientific Committee, and the list of invited speakers reflect the full geographic, scientific, and ethnic/gender/racial diversity of the Clostpath community. There will be ~150 posters presented, divided over two poster sessions. During the plenary presentations, there will also be flash talks for selected poster abstracts. To foster networking interactions, there is a social program that includes a welcome reception/working dinner on the first day of the conference, a conference dinner/party on the final evening, and optional excursions. The objectives for the 11th Conference will be (i) to continue presenting the highest-quality, recent research on pathogenic clostridia in a forum that facilitates information exchange and future collaborations and (ii) to train and inspire young clostridial researchers who will be the next generation of leaders in the field. These objectives will be realized through three specific aims: Aim 1: Invite, support, and encourage the participation of young investigators and underrepresented scientists. Aim 2: Provide a setting that encourages collegial exchange of scientific ideas and sharing of the most current discoveries in the field. Aim 3: Summarize and report highlights from Clostpath 11