Arid environments are characterised by irregular rainfall and temperature extremes, resulting in highly variable resource availability. Small mammals inhabiting such environments are particularly vulnerable to unpredictable energy and nutrient supplies. Reproduction in these species is thus governed by environmental cues such as rainfall, photoperiod and temperature as well as food availability. The aims of this study were to document the timing of reproduction in a desert dwelling small mammal and to identify the environmental cues that may be responsible for the control of reproduction. Specimens of Rhabdomys pumilio were live trapped and observed on a monthly basis near the Gobabeb Training and Research Centre. Occurrence of a perforate vagina or pregnancy in females and scrotal testes in males were recorded, and related to climate and food availability. Males were reproductively active throughout the year, while females stopped reproducing for a short period in winter. Reproduction of both male and female R. pumilio in the Namib can be described as opportunistic, with environmental factors (food availability and climate) being less of a constraint in males compared to females. Keywords: resource use, environmental controls.