Description of the value of cytology in the ambulant diagnosis of the thyroid gland bases on more than 4000 aspiration-punctions of thyroid gland (Wohlenberg and Pfannenstiel 1974). The indications and contraindications of the aspiration-punction are specified; the scintigraphic cold area is elaborated as a domin of the aspiration-punction. The applied technique and classification of the cytological diagnoses are 99 per cent identical with the histological diagnoses. Because of the large number of pathological modifications of the thyroid gland that have been identified as definitely benign a great many operations can be avoided. The knowledge of the history and the clinical results resp. of the course of the disease prevents delay of urgently indicated operations in cases of uncertain cytological diagnoses.