A specific red cell adhesion test was done in 243 patients with carcinoma of the cervix uteri and showed the presence of isoantigens in only 27.16% of the patients with infiltrating squamous cell carcinoma. There was a gradual loss of isoantigens during the development of carcinoma. The test can be usefully employed in studying the evolution of the disease. The negativity of the test was found to increase as clinical severity of the disease increases. Also, the highest percentage (57.57%) of retained isoantigen was found in large-cell nonkeratinizing carcinoma, a well-differentiated type for the cervix. Follow-up studies suggest that the loss of antigen indicates probably metastasis and a poor prognosis.