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In deserts, rainfall is rare and often irregular, and this directly conditions the growth, flowering and fruiting of plants. Consequently, food can become seasonally scarce for plant-eating vertebrates. The relationship between the reproduction of rodents, rainfall, and plant production has been partly studied in some Asian and African desert regions, but not in Saudi Arabia. We therefore sought to define the breeding periods of the most common rodent in that country, Gerbillus cheesmani. More than 540 specimens were collected during 16 consecutive months between November 2001 and February 2003. As expected, the reproduction of mature males and females showed significant monthly variation directly correlated to rainfall. Most young were captured 2 months after the peak in pregnancy. The reproduction of this species was clearly seasonal in Saudi Arabia, unlike other desert regions where many rodents reproduce more or less throughout the year. Furthermore, both sexes reproduced synchronously, whereas in most other countries, males become reproductive 1-2 months before females. Lastly, reproduction coincided with the rainfall during the study period, but not with the average pluviosity of the country. This indicates that all the individuals responded quickly to the local conditions.