The authors selected methyl chloroform as the prototype of a chlorinated solvent widely used in aerosol products. The review of the literature revealed that methyl chloroform, when introduced as a general solvent, was a significant improvement over the more toxic chlorinated solvents such as carbon tetrachloride, chloroform, and trichloroethylene. The lower level of toxicity of methyl chloroform compared to other chlorinated solvents was confirmed in the original investigation describing acute toxicity in mice and dogs. Mice of the inbred strain Balb-C were caused to inhale methyl chloroform in concentrations of 500 ppm, 1000 ppm, and 2000 ppm for 90 min/day, 6 days/week, for 1 week, 60 min/day, 6 days/week for 2 weeks, and 30 min/day, 6 days/week for 3 weeks. Exposed mice, with controls, were examined for pulmonary function, lipid, phospholipid, and glycogen content of livers and for histologjcal changes attributable to the exposures.