The measurement of steroid hormones in saliva presents a number of attractive opportunities to physical anthropologists and human biologists in areas including reproductive ecology, growth and development, behavioral physiology, and nutrition. Among the key advantages of salivary steroid assays, as opposed to plasma or urinary assays, are the noninvasive and nondisruptive nature of sample collection. Significant disadvantages exist as well, stemming from the increased level of assay sensitivity required and the need for carefully controlled sample collection. Methodological aspects of research design, sample collection and handling, and data analysis and interpretation in the use of salivary steroid assays are discussed in detail, with special attention given to commonly overlooked but potentially crucial considerations. A review of potential applications within physical anthropology includes the use of testosterone assays in studies of male reproductive function and aggressive behavior; the use of adrenal androgen assays in studies of human growth and maturation; the use of cortisol assays in studies of stress physiology and limbic system arousal; and the use of ovarian steroids in studies of female reproductive function.Steroids, as a class of biologically active molecules, are among the most potent and pervasive regulators of vertebrate physiology. They help to regulate basic energy metabolism, both catabolic mobilization of energy and anabolic accumulation of tissue; they serve as primary regulators of adolescent growth and reproductive maturation; they directly determine primary and secondary sex characters; they are crucial in the regulation of adult reproductive function; and they help regulate mineral and electrolyte balance. They are also implicated in the control of libido, aggression, maternal behavior, stress, learning, personality development, and psychopathology. Along with primary sites of production in the gonads and adrenals, and sites of peripheral conversion throughout the body, including skin, muscles, adipose tissue, kidneys, lungs, and liver, they appear also to be synthesized directly in the brain (Le Goascogne et al., 1987). As a group, steroids readily permeate the blood-brain barrier and thus provide one of the primary links between systemic physiology and the central nervous system. It is little wonder, then, that steroids have been the object of intense scientific interest, that several primary research journals restrict themselves exclusively to the chemistry and biology of steroids, or that research reports focusing on steroid physiology are found in journals from fields as diverse as nutrition, psychology, neuroscience, anthropology, social deviance, and child development.The great proliferation of research into steroid physiology dates from the development of reliable assay methods in the 1960s. Berson and Yallow's Nobel Prizewinning technique of radioimmunoassay allowed accurate measurement of circulating steroids in serum and urine. Later outgrowths of this technique all...