To quantify the independent impact of potential risk factors for nickel contact allergy (NCA), a multifactorial Poisson regression analysis of standardized anamnestic and patch test data (with nickel sulfate, 5% in petrolatum) was performed, comprising 74 940 patients assessed in the 33 German and Austrian contact dermatitis units of the Information Network of Departments of Dermatology (IVDK) between 1992 and 2000. NCA was observed in 15.5% patients. Female sex was the strongest risk factor (prevalence ratio 3.74, 95% CI: 3.51-3.98). Risk increased monotonically and significantly with decreasing age. Atopic dermatitis was not a risk factor. The year of patch test had no influence on NCA risk. Significant variation of risk between occupations was observed. In conclusion, our multifactorial analysis was able to quantify the impact of established risk factors and additionally address other, e.g. occupational, factors yet unidentified.