We examined the long-term effects of a behavioral intervention on the psychological distress of patients recently diagnosed with localized cancer, who were being treated at Hadassah University Hospital. All 116 patients who met the inclusion criteria (49 men and 67 women) were randomized into an intervention group and a control group on a 3:1 basis. The intervention chosen was Progressive Muscle Relaxation with Guided Imagery, which is intended to decrease psychological distress and increase the patient's sense of internal control. The Brief Symptom Inventory (BSI) and the Impact of Events Scale (IES) were used to assess psychological distress within 1 month of diagnosis, 3 months later (shortly before starting intervention), and 6 months after the end of the intervention. At the final assessment, the effect of the behavioral intervention on psychological distress was positive. The effect was relatively modest but statistically significant when assessed in terms of the Global Severity Index (GSI) (a decrease of 2.3 points in the GSI of the treatment group as compared to an increase of 1.2 points in the GSI of the control group P=.005). Despite these moderately positive findings, we suggest that the results might be more meaningful if cancer patients are first screened for psychological distress to exclude those with a low distress level that does not justify intervention, and only then randomized for participation in the study.