AbstractA nonparametric method is developed to estimate the minimum dosage level required to induce a given response rate in an experiment. The only assumption used about the response rate is that it is a nondecreasing function with respect to the dosage level. Let nisubjects be independently tested at dosage level xix1x2xk. This paper presents methodology for the estimation of the smallest i such that the response probability at xiis no less than a required level p. A comparison with well‐known nonparametric methods shows that this method is better in some cases. A design of minimum required sample size for a given accuracy is also develope