In recent years there has been an increasing interest in the effects of water temperature changes on the structure of marine populations. During the 1970s the burrowing starfish Astropecten jonstoni was present in large numbers along the southeast of Sardinia (Italy). When investigations were resumed in 1999 fewer active individuals could be found than in the 1970s, with anecdotal evidence suggesting an increase in sightings of dying animals on the sand surface. These observations, combined with a hitherto unknown susceptibility to handling stress, caused us to investigate the effect of water temperature, salinity and individual size on A. jonstoni survival. Results indicated that significantly fewer starfish were affected by a wasting disease when kept at 12° compared with individuals maintained at 20°C and 25°C regardless of salinity (28 or 35 ppt) and that smaller starfish were less affected. Microbiological analysis revealed that, amongst other species, bacteria of the genus Vibrio, which have been associated with diseases of stressed marine invertebrates, were present in both field and laboratory animals.