Optimized tolerance design of DC-DC switching regulators is discussed in this paper. The tolerance design of analog control feedback compensators for DC-DC regulators is considered. Given the desired tolerances on dynamic performances of the closed loop regulator, in terms of crossover frequency and phase margin, a genetic algorithm (GA) seeks the set of values of parameters with maximum tolerance, falling within a region of acceptability (ROA) determined by means of interval analysis (IA). The joined GA-IA approach is applied to the design of a voltage-mode controlled regulator.