This review surveys evidence relevant to the proposition that psychobiologic factors may influence the progress of infection with human immunodeficiency virus Type 1 (HIV-1). Little research has directly examined the influence of psychobiologic factors on the pathogenetic mechanisms underlying HIV progression. However, basic research in neuroimmune interactions indicates that activation of the sympathetic nervous system and hypothalamic-pituitary-adrenal axis can influence several immunologic processes relevant to HIV pathogenesis and the body's ability to resist the progress of infection. A small number of observational natural history studies indicate that certain psychosocial characteristics may be associated with differential disease progression (e.g., subjective responses to highly threatening events, and inhibited psychosocial characteristics). We address some of the methodologic and conceptual issues critical to the interpretation of current results as evidence that psychobiologic processes influence HIV progression, and we conclude by highlighting promising areas for future inquiry.