The Fifth International Workshop on the Enzymology and Molecular Biology of Carbonyl Metabolism was held at Purdue University in June, 1990. This represents the fifth time that I had the privilege of organizing the scientific program. It was the first time that I actually hosted the meeting. I wish to salute my four previous co-organizers and the thousands of scientists who have hosted other meetings. It is much easier to arrange the scientific program and edit the proceedings. No local organization could occur without the help of ones research group and, in this case, my wife. I sincerely thank Esther and my research group for their advise and help. At this Workshop, similar to the preceeding ones, much new information was presented. It was apparent how molecular biological techniques were influencing the direction of the research on the three families of enzymes discussed. It also was apparent that not all biochemical problems could be solved by using these techniques. Many of the presentations showed how important advances still could be made using more traditional biochemical approaches.