Proceedings from the International Symposium on Antibiotic Resistance 1979, the fourth volume in the series of material edited from the Smolenice symposium, is a continuation in the tradition of communicating new scientific results on a currently important and interesting problem. It concerns not only human and veterinary medicine and practice, but also such important fields of contemporary biology as molecular biology and genetics. Indeed, in both these disciplines, we have recently noted a strong and dynamic development of scientific knowledge directed toward such outgrowths of the study of plasmids as gene manipulations, transposons, and transposition, as well as the evolution of plasmids in general. Because of a very real global development of resistance to the newest antibiotics, and the active participation of experts from medical science and practice, it was reasonable to separate the medical part of the program from the theoretical one. Consequently, priorities of the fourth symposium were transposons and the transposition of resistance of to antibiotics, with their serious impact on epidemiology, the resistance of Pseudomonas aeruginosa, that is becoming a prominent nosocomial pathogen, the ecology and epidemiology ofR plasmids, and, last though not least, the computer-assisted surveillance of resistance to antibiotics.