In wireless communication systems, antenna diversity is commonly used to combat the effect of fading and reduce the impact of cochannel interference. The equal gain combining (EGC), which in practical, is easily to implement and less complex in comparison of others diversity schemes, is generally employed. In this paper a new expression of outage probability of a wireless communication system employing EGC in a nonGaussian multipath fading environment is studied by modeling fading channels as a spherically invariant random process (SIRP). The main prominence of the SIRP is that it retains all Gaussian-like properties and has the Gaussian process as a special case. An analytical expression derived for the outage probability and some numerical results in the case of identical and nonidentical interferences can be shown that SIRP can be used to model fading environment in wireless communication systems and also includes Gaussian environment as its special case.