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Does stress impair and can relaxation techniques enhance human immune function? This paper is the first published study in which the investigators used the statistical tool of meta-analysis to examine these important questions. Meta-analysis searches for consistency and aggregate statistical significance among the findings of a collection of experimental studies, many of which contain conflicting results. Dutch investigators used meta-analytic techniques to examine the findings of 24 stress studies and 10 relaxation studies. Inconsistency of study designs limited the ability to pool the findings for the analysis because many studies were not comparable. Furthermore, methodological inadequacies of many of the primary studies eliminated them from the analysis. The meta-analysis permits the determination of consistency of direction of change as well as statistical significance. Among over 20 immunologic variables in the stress studies and 5 immunological variables in the relaxation studies, only a few showed both a consistent and a significant pattern. Stress was associated with consistent and significant declines in interleukin-2 receptor expression and increases in Epstein Barr Virus antibody titers—both suggesting relative immunosuppression. Relaxation was associated with consistent and significant changes in only one of 5 immunological variables, salivary immunoglobulin A levels, which were increased by relaxation training. This study underscores the methodologic deficiencies in this body of research. However, the results are suggestive that psychosocial stress can suppress and relaxation training can enhance some parameters of human immunity under certain circumstances. There is a need for more replication studies. Because the popular media give more attention to the positive studies than to the negative ones, the public has tended to accept uncritically the idea that stress impairs immunity and that relaxation can enhance it.