An analytical method for investigating slotted ALOHA land-mobile networks is presented. The probability of successful reception and throughput is assessed for a single base station, taking account of contending transmissions and receiver noise. Receiver capture is assumed to occur if the received signal power exceeds the joint interference power by a certain margin, called the receiver threshold. Rayleigh fading and UHF groundwave propagation are considered. Results are extended for a cellular network considering the interference from packet transmissions in other (co-channel) cells. It is seen that in packetswitched cellular nets, frequency re-use distances may be substantially smaller than in circuitswitched (CW) telephony networks, where each cell has to be safeguarded continuously from cochannel interference. Moreover, a technique to assess the throughput of ALOHA networks with multiple, geographically-separated base stations is presented and numerical results are given for uniform Poisson-distributed packet transmissions in the service area.