ESEMPI DI ARCHITETTURA, VOL. 6, N. 2, contains 13 articles that have in common to analyze different types of tourist conflicts in European and Mexican urban destinations. From these texts, in this Introduction to the monograph, a general reflection is made on the subject, its consequences and challenges. It is, without a doubt, a complex phenomenon. But the enormous forecasts of growth in world tourism force to see these conflicts as warnings before a situation that can be unsustainable if it is not resolved.