The "Computational Modeling in Biology" Network (COMBINE) is an initiative to coordinate the development of the various community standards and formats in systems biology and related fields. The fourth annual COMBINE meeting is hosted by the U900 Sysbio group and will take place at the Institut Curie, from Monday September 16 through Friday Sep. 20, 2013. COMBINE is a workshop-style event with oral presentations, posters and breakout sessions. The first day of the meeting will be dedicated to presentations of modelling approaches in biology either not currently covered by our efforts, or using them in new or innovative ways. Oral presentations will be selected from the submitted abstracts. Please note that attending this day is free of charge (registration is mandatory, though). More info at: http://co.mbine.org/events/COMBINE_2013 Registration: http://binom.curie.fr/combine2013/