 Chair of Scientific Organizing Committee of workshop "Ergodic Concepts in Stellar Dynamics", Geneva, 1993; Local Organizing Committee of workshops "The Chaotic Universe", Rome, 1999; “Fermi and Astrophysics”, Rome-Pescara, 2001; IX Marcel Grossmann meeting, Rome 2000.Chair of 'Chaos' Parallel sessions at Marcel Grossmann Meetings, Jerusalem, 1997, Rome, 2000, Rio de Janeiro, 2003, Berlin, 2006.Paris, 2009.