Two classes of Gamma Ray Bursts have been identified so far, characterized by T 90 durations shorter and longer than approximately 2 seconds. It was shown that the BATSE 3B data allow a good fit with three Gaussian distributions in log T 90 [4]. In the same Volume in ApJ. another paper suggested that the third class of GRBs is may exist [11] . Using the full BATSE catalog here we present the maximum likelihood estimation, which gives us 0,5% probability to having only two subclasses. The MC simulation confirms this probability.