The increasing interest on the possibility of accessing information anytime, anywhere, associated with the development of modern portable equipments, is stimulating the mobile network evolution. This is a gradual evolution, from the firt mobile network generation, 1G, towards the fourth generation, 4G, passing through 2G, 2.5G, and 3G. Higher video, voice and image transmission capacities are reached on each generation. GSM (Global System for Mobile Communications) is a 2G technology, while GPRS (General Packet Radio Services) is a 2.5G technology. This work compares the capacity of both GSM and GPRS networks. Experimental results obtained through simulation are described, in which the number of mobile stations as well as the traffic generation rate are varied. The main results show that with the GPRS there is a greater number of mobile stations transmitting simultaneously, as it allows a multi-slot allocation. There is also an performance analysis of the GPRS environment. The delay, jitter and throughput are the performance parameters analyzed. The GPRS ideal empirical release time is indicated.