The results of a NIOSH health hazard evaluation of the effects of occupational exposure to emissions from Hawaiian volcanoes were discussed. The evaluation was requested by the National Park Service because of concerns of Park employees about being exposed to volcanic emissions at Hawaii Volcanoes National Park (HVNP) on the island of Hawaii. A similar request was received from the Hawaii County Civil Defence Agency. Breathing zone samples were collected from park employees at six sites in HVNP and analyzed for sulfur- dioxide (7446095) and other irritant gases. Area air samples collected at vent sources throughout the park and at areas where Hawaii Civil Defense workers had been stationed for prolonged periods, usually at places where roads and trails had been blocked by lava flows, were analyzed. The analyses were limited to sulfur- dioxide and other irritant gases because the volcanoes were not active at the time of the survey. Park records were reviewed to obtain information about incidents in which tourists or employees experienced health effects as a result of volcano emission exposures. Forty three park employees completed a symptom questionnaire. Sulfur-dioxide was not detected in any of the breathing zone samples. Long term area air samples indicated ambient sulfur-dioxide concentrations of 0.8 to 5.0 parts per million (ppm). A short term air sample obtained on a rock pile that covered a vent measured 4.1ppm sulfur-dioxide. These were considered to be minimal exposures since the volcanoes were inactive at the time. At least half of the park employees reported symptoms such as headache, eye and throat irritation, cough, and phlegm production. Chest tightness, wheezing, and dyspnea were also frequently reported. Area air samples obtained at the civil defense roadblocks indicated the presence of hydrogen-chloride (7647010) at concentrations ranging up to 10 to 15ppm. These exposures were associated with acid mists generated by lava contacting seawater. The author concludes that many park employees are experiencing acute irritant symptoms that are consistent with exposure to sulfur- dioxide and other irritant gases from volcanic emissions. A more detailed industrial hygiene survey including a medical evaluation of the HVNP employees is planned.