This volume, which follows the recent publication of our Fish Atlas, covers all the larger Crustaceans. It documents the arrival in the past hundred years of sixty species of shrimps, lobsters and crabs - the quasi totality of tropical origin - all new to the Mediterranean Sea. The transfer of exotic species is as ancient as maritime transport: in Phoenician times organisms from distant shores, transported on ship hulls and in ballast across the Strait of Gibraltar, and then from port to port around the Basin, were certainly introduced to the Mediterranean world on more than one occasion. What is striking is the rate of recent arrivals: 60 newcomers in only 100 years is a very high number compared to a pool of 350 autochtonous decapod species ! The opening of the Suez Canal, the development of shipping traffic and of mariculture operations all provided major vectors to this latest wave of introductions. Whether or not global warming will accelerate this latest upsurge of tropical invasions is much open to question. CIESM, the Mediterranean Science Commission, could only take a keen interest in a process which has major, yet poorly studied, impacts on the marine biodiversity of the whole region. This Atlas is the outcome of five years of work by our expert group on crustaceans who carefully analysed hundreds of records, ranging from the early Cambridge expedition to the most recent sightings signaled by the vast CIESM network of biologists. Three-quarters of the exotic species identified are of Indo-Pacific origin, most of them Erythrean migrants having crossed the Suez Canal, and now largely settled in the eastern Mediterranean Basin. The other exotics were introduced by shipping or mariculture transfer. This finely illustrated Atlas aims to be an essential reference for specialists and non-specialists alike, who will find distribution maps, key references, plus relevant biological and geographical annotations for each species, as well as an abundant bibliography.