A covering letter and a questionnaire covering the diagnosis and treatment of thyrotoxicosis in childhood was circulated between October 1992 and February 1993 amongst 672 European members of the European Thyroid Association (ETA) and members of the European Society for Pediatric Endocrinology (ESPE). Almost 50% replied to the letter and 99 individuals or groups from 22 countries completed the questionnaire. A consensus was reached on the use of total thyroxine (T₄) and/or free T₄ and thyrotropin as routine diagnostic tools. Two-thirds included total triiodothyronine (T₃) and/or free T₃ and 32% used a thyrotropin-releasing hormone test. Surprisingly, thyroglobulin autoantibodies were used as a routine test by 78%; 63% included thyrotropin receptor antibodies and 60% microsomal antibodies, whereas only 50% measured thyroperoxidase antibodies. For thyroid imaging, 40% performed a thyroid scintigram and 56% measured the size of the thyroid gland by ultrasound. Antithyroid drugs (ATD) were the basic initial treatment of choice given by 99% of the respondents for children with uncomplicated Graves' disease. Carbimazole, methimazole and thiamazole were the most frequently used drugs, with a median initial dose of 0.8 mg · kg^-1 day-l. Two-thirds added beta-blockers and a few used sedatives. The ATD dose was adjusted for each patient by 39%, whereas 56% combined ATD with T₄ for long-term treatment; 84% gave treatment for a fixed period (44% for 1-2 years). Surgery was considered the treatment of choice in children with an adenoma (83%), with a nodular (53%) or large goiter (16%) and recurrence after ATD (14%). Radioiodine was the treatment of choice by 18% of the respondents for patients with recurrence after surgery and recurrence after ATD (7%).