The Chihuahuan Raven (Corvus cryptoleucus) is abundant and conspicuous throughout its range, but much remains unknown about its breeding biology and social system. We studied the breeding biology of this species in southern New Mexico in 2000 and 2001, and hypothesized that environmental variability of desert habitats represents a major selective force. We predicted that variable food supplies and limited nest sites might select for cooperative provisioning of young similar to behavior in several other members of the genus Corvus. We examined nesting behavior and social relationships of nesting groups. Nest observations revealed that both males and females incubate eggs, brood nestlings, and feed young. Nesting pairs were primarily territorial in the immediate vicinity of the nest, but occasionally tolerated intruders, and at other times were joined by the intruders in communal mobbing of potential predators. Average group size near the nest was 1.7 birds and we did not detect auxiliary birds at or near the nest. We found no sign of cooperative breeding in the population of Chihuahuan Ravens we studied. However, we did find cooperation in predator defense within groups of nesting ravens.