Chromosomul pattern and cell proliferation studies were performed on blood samples of 20 male and female control subjects as well as 19 male and female primary utrophic rhinitis (AR) patients. The chromosome anomalies were noticed to be increased significantly in AR patients in whom the chromosomes were affected mainly in those regions containing the genes regulating immunoglobulin synthesis. Accordingly, a relative immunodeficiency was proposed; an opinion which was supported by cell proliferation studies which revealed an attenuated ability of AR leukocytes to undergo an adequate hlastogcnic response when stimulated with the plant let tin ph ylohacmagglutinin. The results suggest a genetic basis of the disease despite the negative family history in all cases studied.