Salivary immunoglobulin A, secreted by the local secretory immune system of the upper respiratory tract, plays an important role in the protection of infections. Psychoneuroimmunological studies postulating influences of mood states on secretion of immunoglobulin A are reviewed and discussed with regard to their internal and external validity. The results on the influence of emotional stress are heterogeneous: Lower, as well as higher, as well as unchanged secretions of salivary immunoglobulin A have been reported. This may be due to insufficient control of intervening variables, to different methodologies and to selection of non-representative subject populations, so that the relationship between emotional stress and secretion of salivary immunoglobulin A remains still under discussion. On the other side, two studies indicate that mental relaxation procedures can lead to increased secretions of salivary immunoglobulin A in comparison to vigilance task, finger touching or no explicit treatment. However, more research is required, especially on the size and duration of the induced effect. Future psychoneuroimmunological research strategies should consider to a greater extend emotion-specific and person-specific aspects, methods used in experimental virology and mediators between mood and salivary immunoglobulin A.