Experimental work was undertaken to provide a basis for appraising the hazards which may attend the use of 2-nitropropane ((CH3)(2)C(H)NO) as a solvent. Skinner reported that workers complained of severe headache and gastroenteric disturbances while using 2-nitropropane on a damp day in a poorly ventilated shed. The results of analyses, performed presumably on another day, suggested that the atmospheric concentrations that gave rise to the complaints may have been of the order of 15 to 45 parts per million (ppm). The physical properties of this nitroparaffin and the toxicity shown by it when it was administered orally to rabbits have been reported previously. At a pressure of 745 mm. of mercury and a temperature of 25 C. (77 F) air saturated with volatilized 2-nitropropane would contain 95.8 mg. per liter since at this temperature the vapor pressure is 20 mm. Under similar conditions the concentration of 1 mg. of 2-nitropropane per liter of air is equivalent to 280.1 ppm. Its odor was detectable at 1.05 mg. per liter (294.0 ppm) but not at 0297 mg. per liter (83 ppm). The work described in this article was sponsored by the Commercial Solvents Corporation, whose financial aid is gratefully acknowledged, as is also their assist- ance in supplying the material for investigation.