ABSTRACT Human subjects were exposed to vapors of Stoddard solvent and 70 solvent to ascertain (a) the olfactory threshold@ determined in a series of 30-second exposures@ and (b) whether appreciable irritation was experienced during continuous 30-minute exposures. The maximum concentration of Stoddard solvent was 60 mg/1 (100 ppm) the value currently suggested by the American Conference of Governmental Industrial Hygienists. The maximum value of 70 solvent used was 0.35 mg/1 (64 ppm). A flow-dilution olfactometer system was used for all exposures. The olfactory threshold for Stoddard solvent@ determined in tests of 47 subjects@ was 0.002 mg/1. The threshold for 70 solvent was 0.003 mg/1 (48 subjects). Subjective reports of eye@ nose@ and throat irritation@ as well as polygraph records of eyeblink@ swallowing@ and respiration rate@ were recorded during 30-minute exposures to 0.60 mg/1 Stoddard solvent@ 0.35 mg/1 70 solvent@ or to control air. There was a higher incidence of eye and nose irritation reported by subjects exposed to the solvents than in those exposed to air only@ but the effect was mild. There were no differences between control and solvent-exposed subjects with respect to eyeblink@ swallowing@ or respiratory rates. Post-exposure examination of subjects using a test of eye-hand coordination (Purdue Pegboard Test) also showed no difference between control and experimental subject.