During the last decade or so vaccine development has been facilitated by rapid advances in molecular and cell biology. These have laid the foundations of a new generation of vaccines exemplified by subunit vaccines produced through gene cloning and by synthetic peptides mimicking small regions of proteins on the outer coat of viruses. Such peptide~ are capable of eliciting virus-neutralizing antibodies. Unfortunately, subunit and peptide vaccines are only weakly or non immunogenic in the absence of immunological adjuvants that are known to augment specific cell-mediated immune responses to the antigens and to promote the formation of protective antibodies. This book contains the proceedings of the 4th NATO Advanced Studies Institute (ASI) "Vaccines: New Generation Immunological Adjuvants" held at Cape Sounion Beach, Greece, during 24 June -5 . July 1994 and deals in depth with both theoretical and practical aspects of vaccinology. These include the role of antigen presenting cells in the induction of immune responses. immunopotentiation by a variety of new generation immunological adjuvants and vaccine carriers. and recent advances and perspectives in experimental vaccines as well as vaccinatioll with nucleic acids. We express our appreciation to Dr. K. Dalsgaard and Dr. J. L. Virelizier for their cooperatioll in planning the ASI and to Mrs. Concha Pening for her excellent production of the manuscripts. The ASI was held under the sponsorship of NATO Scientific Affairs Division and generously co-sponsored by SmithKline Beecham Pharmaceuticals (Philadelphia).