An easy-to-use standardized instrument is needed for the clinical assessment of the severity of occupational hand eczema by dermatologists as well as occupational physicians. The Osnabrueck hand eczema severity index (OHSI) was developed for this purpose and the interobserver reliability investigated. The clinical severity was evaluated on the basis of the extension or clinical characteristics of six morphological characteristics. For the validation of the OHSI, hand eczema in 28 patients was investigated independently by one dermatologist and 2 occupational physicians. The agreement between the observers was determined by using kappa values, Kendall's coefficient of concordance, the intraclass correlation coefficient (ICC) and the 95% limits of agreement. The ICC for the total OHSI was 0.80 and the estimated limits of agreement (-3.6 and 3.0) were sufficiently small to expect that ratings according to OHSI performed by independent observers of different medical specialities should produce similar results. It could be demonstrated that the use of the OHSI is simple and practicable. The interobserver reliability for the summary score is good. OHSI seems a reliable tool for assessing the severity of occupational hand eczema.