OBJECTIVE: To comprehend the stigma against people with mental disorders still persists in the culture of general hospitals and acts as a limiting factor in the implementation of psychiatric units in general hospitals in Brazil. METHODOLOGICAL PROCEDURES: A qualitative social survey was outlined based on action research strategy as of the agreement to adopt a psychiatric unit in a general hospital in Taubaté, Southeastern Brazil. Data was obtained through interviews, participant observation and talks on the psychiatric unit project given to the hospital's clinical staff. RESULTS: The investment made by the healthcare authority enabled the stigmatizing conceptions (violence, moral weakness and untreatability) present in the hospital culture in question to be resignified by means of clinical and sanitary discussions, which enabled the implementation of the psychiatric unit. The analysis showed that these concepts persist in this context because of a healthcare system that limits the access of people with mental disorders. CONCLUSIONS: The attitude of the healthcare authority, who decided to adequately fund the general hospital's psychiatric unit and exerted his influence over the hospital, was decisive for the outcome of the case. The main difficulty in implementing psychiatric units at general hospitals is not the overcoming the existing stigma in the culture of general hospitals, but rather a difficulty which is strategic in nature: the lack of an affirmative policy for these units.