to the Animal Models Volumes This volume describes animal models of drug addiction. Because of increasing public concern over the ethical treatment of animals in research, we felt it incumbent upon us to include this general preface in order to indicate why we think further research using animals is necessary. Animals should only be used when suitable alternatives are not available, and humans can only be experimented upon in severely proscribed circumstances. Alternative procedures using cell or tissue culture are inadequate in any models requiring assessments of behavioral change or of complex in vivo p- cesses. However, when the distress, discomfort, or pain to the animals outweighs the anticipated gains for human welfare, the research is not ethical and should not be carried out. It is imperative that each individual researcher examine his/ her own research from a critical moral standpoint before eng- ing in it, and take into consideration the animals' welfare as well as the anticipated gains. Furthermore, once a decision to p- ceed with research is made, it is the researcher's responsibility to ensure that the animals' welfare is of prime concern in terms of appropriate housing, feeding, and maximum reduction of any uncomfortable or distressing effects of the experimental conditions.