This study was designed to evaluate the characteristics of human orbital fat and connective tissue. Two exenteration specimens were studied by light microscopy with special stains. Four distinct regions were identified on the basis of their connective tissue septa, which contained blood vessels and were composed of elastin and collagen types I, III, and IV. Transmission electron microscopy was performed on the opposite orbits. The fibroblasts and adipocytes appeared metabolically inactive and showed no regional differences. The fat was phase extracted from the connective tissue and subjected to biochemical analysis. No regional differences were found in the content of fatty acids and protein. The fatty acids included palmitic acid (22-24.6%), oleic acid (45-51.5%), and linoleic acid (15-18.6%). Despite demarcation of the orbital fat into distinct regions by the connective tissue septa, ultrastructural and biochemical analysis revealed no regional variations in the fat. The diagnostic and therapeutic implications of these findings are discussed.