To systematically study and document regional variations in descriptions of nervios, we undertook a multisite comparative study of the illness among Puerto Ricans, Mexicans, Mexican Americans, and Guatemalans. We also conducted a parallel study on susto (Weller et al. 2002, Culture, Medicine and Psychiatry 26(4): 449-472), which allows for a systematic comparison of these illnesses across sites. The focus of this paper is inter- and intracultural variations in descriptions in four Latino populations of the causes, symptoms, and treatments of nervios, as well as similarities and differences between nervios and susto in these same communities. We found agreement among all four samples on a core description of nervios, as well as some overlap in aspects of nervios and susto. However, nervios is a much broader illness, related more to continual stresses. In contrast, susto seems to be related to a single stressful event.