During a 30-year period 8561 thyroidectomies were performed and 660 new patients presented with thyroid cancer. The number of thyroidectomies performed annually remained relatively constant for the past 20 years but the annual incidence of thyroid cancer increased from two patients in 1963 to 60 in 1992. Possible contributing factors include: altered referral patterns as a result of the introduction of fine-needle aspiration biopsy; an increase in the incidence of occult papillary cancer as a result of performing total thyroidectomy for multinodular goitre; and a background increase of thyroid cancer in the population. Data from the New South Wales State Cancer Registry implicate a background increase in the incidence of thyroid cancer in the population as a major contributing factor.