Astropecten irregularis is an important predator in the structure and organization of subtidal soft-sediment communities. Seasonal changes in the population dynamics of A. irregularis and its prey exhibit complex interactions with each other and the physical environment e. g. substrate, seawater temperature and tides. The dietary characteristics of A. irregularis has been examined at sites throughout the southern and western coastal waters of the British Isles. Although A. irregularis shows a strong seasonal preference for juvenile bivalves e. g. Spisula subtruncata, its diet broadly reflects the relative availability of prey and includes crustaceans, gastropods, polychaetes and echinoderms. During winter starfish migrate off-shore into deep water and during summer they form spawning assemblagesC. hangesi n the arm length (growth) of A. irregularis is seasonal, where maximal growth occurs between mid-summer and mid-autumn. Cluster analysis and multi-dimensional scaling proved to be useful tools in the identification of seasonal patterns in the starfish diet. Laboratory experiments and x-ray radiographs were used to examine prey selection; interactions between prey density, prey survival within the starfish stomach (which varies with predator size) and prey profitability were identified. Capture and ingestion of different molluscan, crustacean and echinoderm prey have been described. Freshly caught starfish exhibited an endogenously controlled quadri-diurnal locomotory activity under continuous darkness, which coincided with expected slack water at high and low tides. In a laboratory flume starfish burrow into the sediment in response to strong water currents and form subsurface aggregations. The distribution and occurrence of the polynoid commensal Acholoe squamosa and its host A. irregularis is also reported.