The ability of skilled physicians to estimate cancer risk in nontoxic goiter was determined by reviewing 235 evaluations of patients referred as thyroid cancer suspects and comparing the diagnostic impressions with the subsequent clinical and histological findings. Of 202 patients classified as "benign" on clinical evaluation, 2% proved to have thyroid cancer. In contrast, 28% of those classified as "suspected of cancer" and 53% of those classified as "probably cancer" did indeed have malignant goiters. Furthermore, although only 63 patients with "benign" goiters were subjected to early thyroidectomy, these included all 4 with thyroid cancer so far identified in this group. These figures indicate that patients with goiter can be divided quite successfully into low and high cancer-risk groups and that preoperative selection is justified.