In January 1996 a total of 270 conference participants gathered for 3 days in Trondheim, Norway, to focus on and to discuss the complex topic of hydrocarbon seals particularly related to deformation zones and to caprocks. The conference was the first in Norway and one of the first in Europe to exclusively address this very important subject. The purpose of the conference was to present some of the most recent research results, to establish state-of-the-art with respect to understanding hydrocarbon seals and to discuss where to go from here to find some of the keys to successful future exploration and enhanced oil and gas recovery. Out of the presented papers and posters, 17 are compiled and published in this volume. These provide a good overview of and an introduction to the numerous aspects covered during the fruitful days in Trondheim.