Introduction. C.N. Slobodchikoff and W.M. Shields, Ecological Trade-Offs and Social Behavior. Theory of Ecological Interactions. C.N. Slobodchikoff and W.C. Schulz, Cooperation, Aggression, and the Evolution of Social Behavior. L.-A. Giraldeau, The Stable Group and the Determinants of Foraging Group Size. G.W. Barlow, Monogamy in Relation to Resources. Ecology of Social Mammals. P.S. Rodman, Resources and Group Sizes of Primates. P.M. Waser, Resources, Philopatry, and Social Interactions among Mammals. K.B. Armitage, Resources and Social Organization of Ground-Dwelling Squirrels. J. Berger, Social Systems, Resources, and Phylogenetic Inertia: An Experimental Test and Its Limitations. Ecology of Social Birds. W.M. Shields, J.R. Crook, M.L. Hebblethwaite, and S.S. Wiles-Ehmann, Ideal Free Coloniality in the Swallows. J.D. Ligon and S.H. Ligon, Territory Quality: Key Determinant of Fitness in the Group-Living Green Woodhoopoe. J.M. Marzluff and R.P. Balda, Resource and Climatic Variability: Influences on Sociality of Two Southwestern Corvids. B. Heinrich, Food Sharing in the Raven, Corvus corax. Ecology of Social Arthropods. G.B. Pollock and S.W. Rissing, Social Competition under Mandatory Group Life. J.Y. Gautier, P. Deleporte, and C. Rivault, Relationships between Ecology and Social Behavior in Cockroaches. G.W. Uetz, Risk Sensitivity and Foraging in Colonial Spiders. T.G. Myles, Resource Inheritance in Social Evolution from Termites to Man. Index.