Background: Diisocyanates are widely used in industry, for example at hospitals as a constituent of Scotch Cast soft casts (3M, Glostrup, Denmark). They are a cause of occupational asthma and have been described as causing cutaneous problems both as irritants and as sensitizers. Objective: The sensitizing potential of diisocyanates has previously only sporadically been described, predominantly in case reports. Therefore, we conducted this study to investigate eventual work-related skin sensitization to diisocyanates in a regularly exposed population. Methods: The nursing staff of an orthopaedic outpatient clinic, consisting of 10 persons, were interviewed and subjected to patch testing using 5 types of diisocyanates and the TRUE Test (ECDRG Standard Series) to elucidate possible other type IV allergies with similar symptoms. Patch test results were evaluated according to the guidelines of the International Contact Dermatitis Group. Results: We found no relationship between exposure time and severity of symptoms. Symptoms were mild, consisting of redness, itching, or both, lasting about 30 minutes. There was no suggestion that they result in any chronic skin problems. One nurse presented a doubtful reaction towards diaminophenylmethane (MDA) and isophorene diisocyanate (IPDI). Nine persons had no reactions to the 5 diisocyanates used in the patch test. Positive reactions were seen to nickel (4/10), thiomersal (2/10), and perfume mix (1/10). Conclusion: Our observations suggest that diisocyanates are primarily irritants rather than sensitizers in the professional setting studied. The skin symptoms of irritation were all mild and temporary.