The SIgA and IgA quantification by radial immunodiffusion was carried out in the saliva of 449 normal individuals, whose ages vary from 1 day to 32 years old. SIgA was determined in an agar plate containing purified serum against SIgA of human colostrum and the IgA in commercial plates containing serum anti IgA. The SIgA values grouped in different age groups were much variable, allowing only to establish minimum critical values for each group. In the saliva of 71 patients IgA was dosed by both methods. The set of obtained data showed significant correlation (p less than 0.05). The dosage of standardized quantities of SIgA and IgA in conventional plates containing serum anti IgA, allowed to establish corresponding values similar to precipitation ring diameter. In this way, it was possible to establish a "critical value" for salivary IgA by the use of conventional plates. Thus, the IgA quantitative determination by radial immunodiffusion with antibody against serum IgA was carried out in saliva samples of normal and atopic individuals (asthma and/or rhinitis). The patients' ages varied from 1 month to 32 years old. The obtained values were grouped according to defined age group. We observed non-measurable values in 70% of the children aged less than 1 month; from then on, the values were increasing, reaching adult levels from the 6th year on. We did not observe differences between the salivary IgA levels of normal and atopic children. In children aged less than 6 months breast and/or bottle feeding (natural, mixed or artificial) there were no differences between the IgA levels observed in saliva.