Empirical studies confirm that the received radio signals in certain cellular systems are well modelled by Nakagami statistics. Therefore, performing relevant systems studies can be potentially useful to a system designer. A very useful statistical measure for characterizing the performance of a mobile radio system is the probability of outage, which describes the fraction of time that the signal-to-interference ratio (SIR) drops below some threshold. A more refined criterion for the outage is the failure to simultaneously obtain a sufficient SIR and a minimum power level for the desired signal. Thus, we derive new expressions for the probability of outage where a mobile unit receives a Nakagami desired signal and multiple, independent, cochannel Nakagami interferers. A salient feature of our results is that, unlike some previous studies, the outage expressions do not restrict the Nakagami fading parameter, m, to strictly integer values. Furthermore, since the received signals in mobile radio also experience log-normal shadowing, we analyze the case where the received signals are modelled by a composite of Nakagami and log-normal distributions. Outage probabilities are computed and graphically presented for several cases. The effect of specifying a minimum signal requirement for adequate reception is found to introduce a floor on the outage probability. It is also found that shadowing in macrocellular systems severely degrades the desired quality of service by increasing the reuse distance necessary for a given outage level.