This is an elegant monograph written in Bucharest, published in Basle, and distributed in Baltimore and London. This international flavor is consonant with the sophistication of the text. Sections deal with electron microscopy and autoradiography of the thyroid (animal and human), in the normal, under various induced conditions, and in several disease states. This represents an effort to correlate ultrastructure and biochemistry to explain the biosynthesis of thyroid hormones. One third of the book is devoted to superb reproductions of tissue sections (conventional, electron microscopic, and autoradiographic) borrowed from the Journal of Cell Biology.