Immunoglobulins in duodenal content were measured by immunodiffusion in children without infection. Two groups were studied: group I with 11 infants 1 to 35 months old without infectious problems and group II with 14 children 3 to 13 years old who one month previously had suffered typhiod fever. Two groups of commercial plates were used both designed to detect low levels. The plate for values of 1 to 10 mg. % was selected for the study. Secretory IgA (IgAS) was determined using a standard of human colostrum. Total proteins were measured by Biuret's method. The values obtained in Group I were: 2.3 +/- 0.44 for IgAS, 4.9 +/- 1.29 for IgM, 2.3 +/- 1.0 for IgG and 461.09 +/- 160.89 mg. % for total proteins. In Group II, in the same order, the values were: 2.28 +/- 0.59, 3.70 +/- 0.98, 1.57 +/- 0.37 and 333.91 +/- 64.63 mg.%. No sataistically significant difference was found for any of the values mentioned when comparison between the two groups was made; therefore, when values for the two groups were added, the final results were: 2.29 +/- 0.35 for IgAS, 4.23 +/- 0.74 for IgM, 1.89 +/- 0.45 for IgG and 389.86 +/- 70.53 for total proteins. Between serum and intestinal IgA (r = 0.11), there was no correlation. No statistical difference was either found when grouped by sexes or ages (less than 3 and greater than 3 years). It is concluded that the method applied allows the use of very small amounts of the sample, avoids the inconveniences of concentration, is available to any laboratory and permits detection of values as low as 0.5 mg. %.