Lateral hostilities among emergency and critical care nurses. Survey in five hospitals of Tuscany Region. Introduction. Lateral hostilities (LHs) are a kind of workplace violence. They are defined as varieties of cruel, rude, antagonistic interactions between people at the same hierarchical level. Nurses are affected by LH from 5.7% to 65%, leading to reduced work motivation, psycho-physical disorders, and in some cases, drop out of the nursing profession. Objective. To quantify the LHs among nurses in the emergency departments (ED) and intensive care units (ICU) in 5 hospitals of Tuscany (Italy). To show the impact on the quality of their psycho-physical and professional lives. Method. Exploratory-descriptive study, through closed-ended questionnaire. Results. 360/444 nurses (81%); 294 (81.6%) were victims of LHs during the past 12 months. Gossiping, complaints shared with others without discussing with the concerned person, and sarcastic comments were the most reported LHs. LHs occur more in EDs than ICUs (respectively 90% and 77%; p=0.0038). No statistically significant differences were observed for gender, age, or years of experience. The 17.7% of nurses asked to be moved from the ward, and 6.9% left it; 6.9% respondents had thought to leave the nursing profession; 235 (65.2%) experienced at least one LHs related disorder during the last year. Most reported symptoms were low morale, anxiety, and sleep disturbances. Conclusions. The incidence of LH and related disorders is high in EDs and ICUs, determining a low professional and psycho-physical quality of life.