Of the techniques which are usually used for the in vitro etiologic diagnosis of determined allergic processes, it is the RAST technique which is most widely used for determining specific antibodies of the IgE class. On the other hand, also of interest is the quantification of total IgE in these patients. We have studied 80 allergic and non allergic patients in order to evaluate the possible correlation between the Prick and the RAST tests applied to different allergens such house dust. Dermatophagoides pteronyssinus and Dermatophagoides farinae. The patients were distributed in four groups in relation to the clinical history and serum levels of total IgE, as follows: Group I: Patients with positive clinical history and increases levels of total IgE. Group II: patients with positive history and normal values of total IgE. Group III: patients with negative history and increased levels of serum IgE, and Group IV with non atopic subjects with normal values of IgE. The results show a high correlation between both tests for house dust mite allergens in the group I. The relation to inferior in the group II. As far as house dust is concerned, there is no correlation between the cutaneous test in the RAST test even in the group with positive clinical history. The data observed with house dust mites suggest a relation between the clinical history and the cutaneous test and also between the RAST and the levels of total serum IgE. These relations are not fund with house dust. It is discussed the validity and applications of both tests to the diagnosis of immediate hypersensitivity reactions to house dust mites and house dust.