Men employed in chlorinated solvents manufacture were followed for 1--4 yr and found to have mean hexachlorobenzene blood levels of 311 ppb in 1974 (n = 50), 312 ppb in 1975 (n = 49), 160 ppb in 1976 (n = 49), and 170 ppb in 1977 (n = 44). Evaluation of urinary porphyrins and several other laboratory test results did not reveal evidence of porphyria cutanea tarda or other adverse effect associated with exposure to hexachlorobenzene. The hexachlorobenzene blood levels were strongly associated with years worked in the chlorinated solvents plant but poorly correlated with environmental measurements.