Nine patients with laboratory-acquired Rocky Mountain spotted fever (RMSF) were seen during the period 1971-1976. Investigation of each case revealed either definite or probable exposure to an aerosol containing infectious rickettsiae; in no case was there evidence of parenteral exposure either by accidental self-inoculation or by tick bite. These illnesses are believed to represent RMSF acquired via the respiratory route; this report emphasizes the aerosol hazard of Rickettsia rickettsii in ...