Second announcement SECA4, "SEminar on Category theory and Applications" Barcelona (CRM): June 6 - 9, 2007. This is the fourth of a series of meetings devoted to category theory and applications. It is intended as meeting point for specialists in category theory and related areas as homological algebra, representation theory, or homotopy theory. Plenary speakers: Denis-Charles Cisinski, Université Paris 13 José L. García Hernández, Universidad de Murcia Ken Goodearl, University of California at Santa Barbara Joachim Kock, Universitat Autònoma de Barcelona Henning Krause, Universität Paderborn Tom Leinster, University of Glasgow Javier Majadas, Universidade de Santiago de Compostela Ieke Moerdijk, Universiteit Utrecht Antonio Viruel, Universidad de Málaga At the request of the organizing committee, the following have accepted to give survey talks, that are specially addressed to the young participants: Ronnie Brown, University of Wales Carles Casacuberta, Universitat de Barcelona Marco Grandis, Università di Genova You will find more information on the following webpage http://mat.uab.es/~seca4/ Some financial support is available for young participants. The deadline to apply for it is March 27. The registration fee is 125 Euros, but there is a reduced registration fee of 100 Euros for those registrating before April 27. If you have specific questions, please send an email to: seca4@mat.uab.es Organizing committee: Pere Ara, Universitat Autonoma de Barcelona Carles Broto, Universitat Autonoma de Barcelona (coordinator) Jose Manuel Casas, Universidad de Vigo Luis Javier Hernandez, Universidad de La Rioja Manuel Ladra, Universidad de Santiago de Compostela Albert Ruiz, Universitat Autonoma de Barcelona Jerome Scherer, Universitat Autonoma de Barcelona Scientific committee: Ronnie Brown, University of Wales Carles Casacuberta, Universitat de Barcelona Jose Luis Gomez Pardo, Universidad de Santiago de Compostela Marco Grandis, Universita di Genova Lionel Schwartz, Universite Paris 13