What will it be like to admit Artificial Companions into our society? How will they change our relations with each other? How important will they be in the emotional and practical lives of their owners - since we know that people became emotionally dependent even on simple devices like the Tamagotchi? How much social life might they have in contacting each other? The contributors to this book discuss the possibility and desirability of some form of long-term computer Companions now being a certainty in the coming years. It is a good moment to consider, from a set of wide interdisciplinary perspectives, both how we shall construct them technically as well as their personal philosophical and social consequences. By Companions we mean conversationalists or confidants - not robots - but rather computer software agents whose function will be to get to know their owners over a long period. Those may well be elderly or lonely, and the contributions in the book focus not only on assistance via the internet (contacts, travel, doctors etc.) but also on providing company and Companionship, by offering aspects of real personalization.