Behavioral and neurological aspects of low level exposure to carbon- monoxide are investigated in a double-blind study with exposure to 5, 35, or 70ppm carbon-monoxide (630080). The behavioral measures of performance include: a compensatory tracking task to measure hand-eye coordination; a visual peripheral monitoring task to measure light intensity discrimination; and an auditory monitoring task to measure tone discrimination. Neurological assessment consists of an analysis of the components of the auditory evoked response. Carboxyhemoglobin levels of 1, 3, and 5 percent are obtained at the end of the fourth hour of exposure for carbon- monoxide exposures of 5, 35 and 70ppm, respectively. Statistically significant decrements in performance are noted at carboxyhemoglobin levels of 5 percent, the NIOSH recommended exposure limit.