Foraging by rice-field rats (Rattus argentiventer) can significantly reduce rice harvest. Rat populations are cyclic responding to season and crop maturity. Rat location also reflects the crop cycle. A study conducted near Sukamandi, Indonesia described rice-field rat burrow systems and patterns of use, and assessed demographics of rice-field rats found in burrows adjacent to rice fields. Burrows ranged from simple short tunnels to complex systems. Most simple systems consisted of a straight tunnel approximately 75 cm long. Mean tunnel length of more complex systems was approximately 300 cm, but a few contained tunnels up to 700 cm. Burrow systems had between 1 and 5 entrances, with 0 to 8 choice-points within the system. A choice-point was defined as any place within the system where the animal could choose a different path (e.g., Y in the tunnel, nest). Number of chambers within systems also varied, ranging from none to six. There was no correlation between rat activity within a system, measured by the closed-hole method, and complexity of the system. Long-term monitoring suggested both male and female rats occupied burrow systems along rice banks, except relatively short periods during spring (March, April) and early fall (September) when burrows were used almost exclusively by females. These periods appear to correlate when high numbers of female rats are gestating and lactating.