When young participants came to New York in July 1970 to speak youths mind on the problems of the era, they rapidly endorsed the nomination of Lars Thalen to be president of the World Youth Assembly. Lars then embarked on the most difficult ten days of his life, struggling to bring order and rational process to a gathering of 500 ebullient and politically active partisans. Opinions about the final result of the World Youth Assembly and the value of its conclusions vary : this programme reflects the enthusiasm and also some of the misgivings of the participants. But there is no dissent on the value of Lars Thalens contribution, nor on the patient firmness with which the Swedish political science student sought to harmonize an inherently discordant gathering.