A total of 181 allergic patients were studied and classified according to the causal antigen, 92 patients were sensitized to the mixed grass pollen, 55 to house dust, 28 to Candida albicans, 31 patients with egg allergy and 25 with milk allergy. All of them presented strong positivity to anamnesis, intracutaneous tests and exposition tests. In all of them the serum total IgE was determined using the radioimmunoassay (RIST) and the antigen specific IgG, following Boyden's passive hemagglutination technique. In 31 patients with pollinosis, 55 with house dust allergy and 25 with sensitization to Candida albicans, the determination of the antigen specific IgG was also carried out following the quantitative precipitation method. The results showed a greater reliability on the hemagglutination as opposed to the determination of total IgE with grass pollen. The hemagglutination was positive in 90.20% and the total IgE was increased in 59.78% of the cases. In patients with house dust allergy the total IgE was elevated in 69.08% of the cases and the hemagglutination was increased in 60.71% of the cases. In those cases of sensitivity to Candida albicans, the total IgE presented higher values in 63.84% of the cases, while the hemagglutination was increased in 21.43% of the cases. In egg allergy,, the IgE was increased in 56.83% of the cases and the hemagglutination in 87.09% of all of the 31 cases studied. In the cases of milk allergy the IgE presented increases in 32% of the cases and the hemagglutination gave higher titers in 56% of all of the 25 cases studied. The results make evident that the hemagglutination should be included in the rutinary diagnosis of allergic diseases as well as the determination of total IgE or antigen specific IgE.