The binary phase manipulated signals, whose auto-correlation functions have small side lobes, are named optimal, as they have a critical role for many types of radio communication systems. With regard to this situation, in the paper we present a genetic algorithm for synthesis of such signals with length N=256. On its base an exhaustive computer search has been conducted. As a result, several unknown until now binary signals with length N=256 and optimal auto – correlation functions have been found.