100 boys between 12 and 15 years of age were subjected to long-term observation. The boys lived under the same conditions (in a boarding school). The 1st of us investigated changes in the singing and speaking voice, the 2nd the anatomical changes in the larynx, the 3rd height, weight and pubertal stages (similar to those of Greulich). We have established that the principal voice changes occur in the 1st 1/2 of pubertal growth, when the increase in height is greatest, but are somewhat in advance of the increase in size of the larynx. Voice changes first show themselves as a lowering of the upper limit of the singing voice, then as a narrowing of the voice range, and lastly as a reviewed extension. The overall characteristics of the individual stages of pubertal and laryngeal change are as follows: Before voice change: boy''s voice, total height of the larynx up to 30 mm, significant increase in height. Beginning of the change (12-13 years): striking loss of high tones, striking changes in the thyroid cartilage, the epiglottis and the vocal cords. Maximal increase in height. Crux of change (13-14 years): significant restriction of the voice range, clearly prominent thyroid cartilage, large epiglottis. Maximal increase in weight. End of change (14-15 years): the voice reaches its full depth, extension of range. Maximal length of vocal cords, and maximal growth of larynx in all dimensions. Further increase in weight, cessation of increase in height.