This report describes two cases of chronic encephalopathy associated with occupational exposure to arsenic fumes from hot pressurized impregnation of wood. Both cases displayed symptoms of cognitive impairment with onset 14-18 months after start of occupational exposure to arsenic fumes. Laboratory confirmation was provided by elevated urine arsenic levels. One patient was hospitalized for apparent psychiatric reasons. Neuropsychologic testing of one case showed typical and relatively mild impairments of new learning, recent memory, and concentration in addition to the psychological symptoms. Symptoms in both cases disappeared following cessation of exposure and return of urine arsenic excretion to normal levels. In future studies of workers exposed to arsenic, documentation of mild impairment of cognitive function should be sought using neurobehavioral test batteries.