During a 5-d period that commenced on August 30, 1987, dry lightning strikes ignited more than 1,500 fires that destroyed in excess of 600,000 acres of California forests. To evaluate the public health impact of the smoke on the general population, all hospital emergency rooms located in the six counties most severely affected by smoke or fire were surveyed. Selected hospital information was abstracted for a 2 1/2-wk period during the fires and during two reference periods. During the period of major forest fire activity, visits of persons with asthma and chronic obstructive pulmonary disease increased in number (observed/expected ratios of 1.4 and 1.3, respectively), as did visits of persons with sinusitis, upper respiratory infections, and laryngitis. A few patients with acute respiratory or eye irritation also visited the emergency rooms. Even recognizing the limited sensitivity of emergency room surveys, the overall public health impact was relatively modest. The increased respiratory morbidity detected in this survey, however, supports the notion that persons with pre-existing respiratory disease represent a sensitive subpopulation, who should be targeted for purposes of public health intervention when exposure to forest fire smoke is likely.