This study summarises historical surveillance data collected from 1977 to 1982 and the results of a field study conducted thereafter (1983-4) in a dipterex packing workshop. The findings suggest that both airborne dipterex and dermal contamination contribute to the inhibition of blood cholinesterase (ChE) and that cases of poisoning in hot seasons can be attributed mainly to dermal absorption. At a level of 0.5 mg/m3, dipterex is shown to lead to a mild but appreciable inhibition of ChE activity. The results also indicate that blood ChE monitoring was sensitive both for long term and short term exposed workers. As a result, the recommendation that the maximum allowable concentration for airborne exposure to dipterex be revised to 0.5 mg/m3, can be regarded at providing only for relative safety.