A trapping survey in Riyadh revealed that the abundant commensal rodent species were Rattus rattus frugivorous (43%), R.r. alexandrinus (18%), R.r. rattus (14%), R.r. flaviventris (12%), Rattus norvegicus (9%), Mus musculus praetetus (3%) and Mus m. gentilulus (1%). R.r. frugivorous was the predominant species in all the nine selected areas. The male: female ratio was 0.4: 0.6 for both R. norvegicus and R. rattus. In both R. norvegicus and R. rattus, the mature rats outnumbered the immature ones.