This paper deals with the problem of optimal scheduling n uninterrupted operations on m machines with respect to a regular criterion. The stability radius ρs(na) for an optimal schedule ns relative to the changes in the vector na=(a1,...,an) of durations of operations Q={1,...,n} is studied. The problem of calculating ρs(na) is reduced to the solution of a non-linear mathematical programming problem. The necessary and sufficient conditions for ρs(na)>0 and for ρs(na)=• are given in the case when ns is the optimal makespan schedule.
