Low-dose iodine-131 of mean activity 1117 MBq was used to ablate post-operative thyroid remnants in 69 patients with differentiated thyroid cancer. Successful ablation was defined as uptake of less than 1% at 48 h and absence of visible image on the post-ablation scan. Ablation by one dose was successful in 95% of patients after total or subtotal thyroidectomy, and 56% of patients after partial or hemithyroidectomy. All patients with uptake of 10% or less on the pre-ablation scan had successful ablation. The results are compared with other reports using low-dose radioiodine ablation and the significance of the findings discussed.