During an 8-year period, 104 patients (19 males, 85 females) underwent surgery for a solitary thyroid nodule. There were 19 (18.3%) malignant nodules and 85 (81.7%) benign nodules. Malignancy occurred in 3 (15.8%) males and 16 (18.8%) females. Pre-operative scanning was performed prior to referral in 59 patients (52 had ultrasound, 41 had isotope scanning; the majority had both). Of the scanned patients, 12 (20%) had a malignant nodule while 7 (15.5%) of the 45 patients who did not have scanning had a malignant nodule. In patients who had an ultrasound scan, malignancy was found in 5 (23.8%) of the 21 solid nodules and 7 (22.7%) of the 31 cystic (or solid/cystic) nodules. In patients who had thyroid isotope scanning, malignancy was found in 6 (17.5%) of the 34 cold (non-functioning) nodules and 3 (43%) of the 7 warm or hot (functioning) nodules. Ultrasound and isotope scanning may be misleading and neither help to differentiate benign from malignant thyroid nodules which require surgical excision.