The concentrations of total protein, albumin, IgA, IgG and IgM in human whole salivas were measured with a solid phase radioimmunoassay before and after physiological stimulation of salivary secretion. The geometric mean concentrations (mg/1) before stimulation were: total protein 1600, albumin 60, IgA 140, IgG 16 and IgM 4.1. Physiological stimulation of salivary secretion caused an increase of the total protein concentration to 2400 mg/1, had little effect on the concentrations of albumin and IgG, but lowered the concentrations of IgA and IgM to 56 mg/1 and 1.7 mg/1, respectively. These findings indicate that a considerable portion of salivary IgA and IgM are produced locally depending on selective transport and that the release from local storage sites is not increased during stimulation as much as the total volume of the saliva.