Smoke exposure measurements among firefighters during prescribed burns in the Pacific Northwest between 1991 and 1994 showed that a small but significant percentage of workers experienced exposure to carbon monoxide and respiratory irritant that exceeded occupational exposure limits. This most often was caused by unfavorable winds or fire behavior and occurred mostly among workers involved in maintaining the fire within the prescribed boundaries. Smoke exposure in such peak exposure situations was up to three times above recommended limits. Exposure to acrolein, benzene, formaldehyde, and respirable particulate matter could be predicted from measurements of carbon monoxide. Electronic dosimeters were the best tool to assess smoke exposure routinely, so long as quality assurance concepts were included in the monitoring program.