Infection. Results.\p=m-\Theattack rates for confirmed and suspected cases combined were 68%, 46%, and 44% among residents in nursing homes A, B, and C, respectively, and 34% among nursing home C staff. A total of 16 cases of pneumonia confirmed by chest x-ray and 6 deaths were identified. The spectrum of illness among nurs- ing home C residents included a new cough in 58 (100%), fever in 37 (64%), sore throat in 14 (24%), and hoarseness in 8 (14%). Staff members at nursing home C were more likely to report hoarseness (P<.001) and sore throat (P<.001). Residents who smoked had onset of illness earlier than nonsmokers (P=.007), which perhaps is related to airborne transmission in a designated smoking room. Conclusions.\p=m-\Chlamydiapneumoniae caused serious morbidity and mortality among residents and morbidity among staff; Cpneumoniae is an important cause of respiratory disease outbreaks in nursing homes, and diagnostic tests must be readily available for early recognition of C pneumoniae infections. JAMA. 1997;277:1214-1218