Summary Background The frequency of nickel allergy varies between different population groups. Exposure regulation has proven effective in decreasing the frequency. Experimental studies with other allergens have shown a significant relation between patch test reactivity and repeated open application test (ROAT) reactivity. Objectives This study was aimed at determining the elicitation threshold in nickel-allergic individuals in a patch test and a ROAT, and comparing the threshold from these two test methods. Methods Twenty nickel-allergic persons were tested with a dilution series of 19 concentrations in a patch test and a dilution series of three concentrations in a ROAT, with duration of up to 21 days. Eighteen persons with no nickel allergy were included as control group for the ROAT. Results The predicted dose which will elicit a reaction in 10% of allergic individuals was calculated to be 0·78 μg nickel cm−2 in the patch test. The threshold for the ROAT (in μg nickel cm−2 per application) was significantly lower than the threshold for the patch test, while the dose–response for the accumulated ROAT dose at 1 week, 2 weeks and 3 weeks was very similar to the patch test dose–response; indeed, there was no statistically significant difference. Conclusions For elicitation of nickel allergy the elicitation threshold for the patch test is higher than the elicitation threshold (per application) for the ROAT, but is approximately the same as the accumulated elicitation threshold for the ROAT. This may be important for risk assessment based on dose–response results from allergic patients.