Mass mortality by tissue necrosis of several species of gorgons was observed during the 1999 late summer on the Liguro-Provençal Mediterranean coasts. We have investigated the occurrence of vibrios on necrosis affected gorgonians Paramuricea clavata and Eunicella cavolinii, and their ability to induce tissue necrosis. Among the 11 strains tested, only 5, belonging to species Vibrio splendidus, V. pelagius and V. campbellii, were able to induce tissue necrosis in a few days. Temperature experiments carried out at 11°C, 18°C and 23°C showed that necrotic disease may occur only at the higher temperature tested. Statistical analysis suggested that, for these thermical conditions, marine Vibrio strains can significantly speed up the necrotic crisis.