Dynamics of immune reactivity in patients with the carcinoma of the cervix was determined. The transformation of their lymphocytes was induced in vitro by phytohemagglutinin (PHA), and the transformation index--a correlate of immunological reactivity--was determined at the following intervals: just before the start of the therapeutic procedure, at the end of the procedure, and every three months afterwards. Very low values of the transformation index, i. e. pronounced immunosuppression, characterized the initial period in all the patients, regardless of either the degree of the disease or the age of the patients. The suppression was prominent during 6 to 18 months following the therapeutic procedures and was overcome earlier in young patients bearing smaller tumors. The results indicate that in tumor-bearing patients a pronounced suppression of immune reactivity occurs after the PHA administration and that it could persist several months after the therapy.