Previous research with individuals undergoing surgery or diagnostic procedures provided a conceptual framework for analysis of radiation therapy, a common form of cancer treatment. The present investigation was designed to document the magnitude of anxiety patients experience in response to one particularly stressful form of radiation treatment. In addition, the change in anxiety responses with repeated exposures and individual differences among patients that may affect their adjustment were explored. In Part 1, gynecologic cancer patients receiving their first internal radiotherapy application were studied. As the time for treatment neared, subjective and physiologic indicants of anxiety and distress among the patients significantly increased. By 24 hours posttreatment, anxiety for all patients remained elevated. These post-treatment data are convergent with other investigations of post-treatment distress among cancer patients, but contrast with data obtained from those receiving treatment for benign conditions. A subset of the women who required two applications of radiotherapy participated in Part 2. These patients continued to respond negatively during the second treatment. Data on individual differences in anxiety responses (i.e., low vs. high anxiety) were obtained in both investigations and suggest that those with low levels of pre-treatment anxiety experience considerable disruption post-treatment.Psychological cancer research has recently focused on the predictors of illness adjustment (e.g., Bloom, 1982), areas of life change following diagnosis and treatment (e.g., Andersen & Hacker, 1983), and anxiety in response to cancer surgery or chemotherapy (e.g., Gottesman & Lewis, 1982;Redd & Andrykowski, 1982). Despite radiation being a primary treatment modality (approximately 350,000 patients are treated annually), it has received little psychologic study. Clinical descriptions of patient reactions are available (Peck & Boland, 1977;Rotman, Rogow, DeLeon, & Heskel, 1977;Smith & McNamara, 1977;Welch, 1980;Yonke, 1967), and they have noted fears of the treatment (e.g., being burned or causing sickness, sterility, or even cancer) and vast individual differences among patients in their psychological reaction to the treatment have been recently found (Andersen & Tewfik, in press).Previous research with individuals undergoing other forms of medical treatment, surgery, or stressful diagnostic procedures, provided a conceptual framework for analysis of radiotherapy. In this research different patterns of anxiety response data have been evidenced, 1 but a decline in the magnitude of patients' self-reported anxiety from pre-to post-treatment is most common (e.g., Cohen & Lazarus, 1973;Johnson, Dabbs, & Leventhal, 1970;Johnson, Leventhal & Copyright © 1984, Lawrence Erlbaum Associates, Inc. Requests for reprints should be sent to Barbara L. Andersen, Department of Psychology, The University of Iowa, Iowa City, IA 52242. 1 Early research examining surgery and recovery experiences from the patient's persp...