To evaluate the effects of low level styrene exposure on psychological performance, picture completion and digit symbol tests (subtests of the Wechsler Adult Intelligence Scale) and the Maudsley Personality Inventory were administered to 12 male laminating workers in a factory producing reinforced fiberglass boats. Airborne styrene concentrations at the workplace were 26 +/- 24 (mean +/- SD) ppm (range 1-77) 3 mon before testing, and 14 +/- 1 ppm (6-46) 2 mon after testing; on the day of testing, the exposure levels, as estimated from levels of styrene metabolites in end-of-shift urine samples, were 22 +/- 17 (mean +/- SD) ppm (range 0-61). Scores on the picture completion test were significantly decreased in these workers, suggesting that psychological performance is adversely affected by occupational styrene exposures at levels of 77 ppm or below.