Radioactive iodine (I) therapy may be used to treat thyroid cancer in end-stage renal disease patients who undergo hemodialysis. Because iodine uses predominantly renal clearance, treatment management in hemodialysis patients may be problematic, and no formal recommendations on hemodialysis currently exist. This work details our experience with treating thyroid cancer with iodine in chronic renal failure patients who require hemodialysis and details the dosimetry results obtained during treatment to ensure that the dose to the bone marrow (BM) was acceptable. We treated 6 patients in the metabolic radiotherapy unit after thyroid stimulation. Two hemodialysis sessions in the metabolic radiotherapy unit were performed at 42 and 90 h after radiopharmaceutical administration. BM toxicity was estimated with activity measurements from blood samples and with whole-body measurements that were regularly repeated during hospitalization and measured with a γ-counter. The patients underwent thyroid and hematologic monitoring to assess treatment efficacy and therapeutic toxicity in the short, medium, and long term. Whole-body activity was reduced on average by 66.7% (range, 60.1%-71.5%) after the first dialysis session and by 53.3% (range, 30.4%-67.8%) after the second. The mean estimated total absorbed dose to the BM was 0.992 Gy for all patients (range, 0.431-2.323 Gy). We did not observe any significant hematologic toxicity, and the clinical, biologic, and ultrasound test results confirmed the success of ablative treatment for most patients. In hemodialysis patients with thyroid cancer, an I activity approximately 30% lower than the nominal dose appears to strike an appropriate balance between absence of BM toxicity and therapeutic efficacy. To avoid overirradiation, we recommend pretherapeutic dosimetry studies for metastatic patients to calculate the amount of activity to be administered. We also recommend dosimetry monitoring during the hemodialysis sessions performed after therapeutic dose administration and under the same conditions.