The authors studied a group of 72 patients with perennial allergic rhinitis. The following parameters were determined: the distribution of T total and T active and B lymphoid populations, non-specific T suppressor activity induced by concanavalin-A, response indices to stimulation by phytohaemagglutinin and pokeweed mitogen and levels of serum IgE. Comparison with 100 healthy controls showed a diminution with respect to the T total lymphoid subpopulation (p less than 0.001) and the suppressor activity (p less than 0.001). There was no significant change regarding the T active and B values and the lymphoproliferative response to the phytohaemagglutinin and pokeweed mitogen. A correlation was seen between the IgE levels (elevated in 62.5% of patients) with the T suppressor activity which was statistically significant (p less than 0.01).