One of the activities of the Ettore Majorana Centre for ,Scientific Culture is the international advanced study courses on scientific topics which are of particular relevance today. The Centre is located in Erice, a mountain town in the province of Trapani in Sicily. At present over seventy Schools of the Centre are active, holding annual or biennial courses, so that about forty courses are organized each year. To date some twenty thou­ sand participants have attended the courses of the various Schools of the Centre. The International Physics Workshop Series has been established to make the contents of the Workshops o'f great topical interest available to those who were unable to attend them. The courses are conducted on an advanced, post-doctoral level. This volume - the proceedings of the session on "Quarks and Hadronic Structure" - is the first of the Series. In September 1975, thirty-three physicists from twenty-one laboratories in nine countries met in Erice to attend the Workshop. The countries represented were: Austria, France, Germany, India, Italy, Poland, Switzerland, the United Kingdom, and the United States of America. The purpose of this Workshop was to bring to­ gether a group of theorists working on various aspects of the quark structure of hadrons to discuss and critically evaluate the present situation. Professor Morpurgo was given the direction of the Workshop. I would like to take this opportunity to thank him most warmly for having accepted this responsibility and for the success of the Work­ shop.