In order to evaluate the reliability of clinical assessment of the thyroid gland, two specialists in endocrinology and two younger doctors independently examined 53 patients twice, and assessed whether they had a diffuse goitre, a multinodular goitre, a solitary nodule or a normal gland. In 30% of the patients all four observers were in agreement, whereas in 47% and 23% of the patients, two and three different diagnoses were given, respectively. Inter-observer variation was determined and kappa values between -0.04 and 0.54 were found. Intra-observer variation was smaller, revealing kappa values between 0.44 and 1.00. The present study suggests that clinical assessment of the thyroid gland may lead to misclassification of the type of thyroid disease, and thereby to a less than optimal choice of therapy.