Population trends for seven genera of rodents were monitored by snap-trap capture rates on a study area (700 km²) in Webb County, Texas, during winter from 1976 to 1986. Population irruptions occurred in 1982 (46-fold) and 1986 (13-fold) for Sigmodon, and in 1982 (17-fold) for Reithrodontomys. Annual variability in abundance was positively correlated between the following pairs of genera: Sigmodon-Reithrodontomys, Peromyscus-Onychomys, Onychomys-Reithrodontomys, and Dipodomys-Chaetodipus. Annual abundance of Sigmodon in winter was positively correlated with rainfall in the prior growing season. Analysis of the distribution of the composite rodent community among five vegetative habitats revealed greater abundance of rodents in the most dense and diverse shrub community (high-density shrub/mixed-grass habitat).