13 of 51 workers developed dermatitis of the hands and face after handling a water-based ink containing a polyfunctional aziridine hardening agent. Improper work practices resulted in skin contamination with the ink and its ingredients. The aziridine hardener contained trimethylolpropane triacrylate (TMPTA). The incidence of dermatitis was highest among the ink mixers who handled the undiluted aziridine (6 of 8 workers affected), was lower among printers who handled ink containing 2 to 4% aziridine (7 of 22 workers affected), and was absent in workers who did not handle ink. The mean latency from first contact with the ink to the development of the rash was 3.2 months among the ink mixers, and 6.2 months among the printers. The present findings demonstrate the risk of handling aziridine hardeners when protective clothing is not properly used and when work practices result in direct skin contact. Further research should be performed to discern whether aziridine compounds themselves, free of TMPTA, can cause dermatitis.