: The present opinions on the therapy with L-thyroxine (L-T4) of non-toxic multinodular, as well as of non-toxic thyroid nodules are rather divergent. This treatment is based on the suppression of TSH secretion from the pituitary. There are no doubts that fine-needle aspiration biopsy (FNAB) performance is the first and--at the same time--the most significant diagnostic procedure in the case of thyroid structural lesions (nodules, goitre, thyroiditis). FNAB performance should--by all means--precede the beginning of L-T4 application for the treatment of non-toxic multinodular goitre or thyroid nodules. The simplicity, clearness and high efficacy, with comparable results in each case, are the core of good diagnostic algorithm. Unfortunately, not all diagnostic algorithms concerning thyroid nodules and multinodular goitre fulfil these important criteria.