This document discusses the criteria and recommended standards for occupational exposure to styrene. Styrene, used in the manufacture of plastics and rubber, can cause depression of the central nervous system and irritation to the skin, eyes, and upper respiratory tract. Topics covered include physical and chemical properties of styrene, worker exposure levels, effects on humans and animals, environmental sampling procedures, and connections between exposure and effect. Methods for worker protection are included. Three appendices provide 1) a method for sampling and analysis of styrene in air, 2) a method for the determination of mandelic acid in urine, and 3) a material safety data sheet.