A familial outbreak (4 cases) of pneumonia by psittacosis in Vall de Uxó (Castellón) during the month of April in 1990 is described. In addition to the epidemiologic, clinical and serologic (complement fixation) studies carried out a survey and serology of 11 healthy controls (neighbors, and employees from a bird shop) were performed. The serum of a parrot recently acquired by the patients (positive at 1/8) was analyzed. The habit of petting the animal was significantly associated with the disease. The patient's response to treatment was good. The titers of antibodies versus Chlamydia psittaci were higher than those of the controls examined and the established threshold for positivity (1/36). In addition to clinical intervention the roles of epidemiology and the participation of veterinary services are fundamental to control this disease the exact prevalence of which is unknown.