Ninety-one exposed and forty-three nonexposed workers are evaluated at five plants, manufacturing polymethyl methacrylate sheets. Significant acute effects developing over the work shift are not detected as measured by symptomatology, blood pressure, and pulse rate. Chronic effects are sought for in past symptomatology, blood pressure, respiratory function testing, hemoglobin and white blood count, urinalysis, and blood chemistry. Data suggest that effects may occur in the higher concentration exposure groups with regard to serum glucose, and blood urea nitrogen, cholesterol, albumin, and total bilirubin values. Also, possible alterations are suggested in skin and nervous system symptomatology, urinalysis findings, and serum triglycerides. Extensive air sampling reveals mean 8-hour time-weighted average exposures by job category ranging from 4 to 49 ppm, for the workers studied, at the individual plants.