Rejuvenation techniques, inspired by a common classical tradition, are described in Caraka (Cikitsā I, 1–4) and in Suśruta (Cikitsā XXVII–XXX), followed up by the Nāvanītaka (Bower Ms., sl.188–200) and by the Astāngahrdayasamhitā (Uttara XXXIX). Valuable mediaeval tīkā comment on the details of these techniques and indeed interesting modern examples of a treatment closely following the ancient medical texts are known.[Contrary to the cure taking place ‘in the open air and in the sun’ (vātātapika), the practice of rejuvenation characterized by the ku is applied indoors in premises called kutī or āgāra, built according to definite rules (site, architecture, etc.). The patient enters at a time astrologically auspicious, after performing certain rites and preparing his mind for a treatment which is as perilous as it is laborious.The rites of the operation and the unusual type of abode, difficult to interpret, permit, however, an examination of the textual data in a different light from that of the scholiasts themselves, who remain very guarded, and even obscure, on important points of detail. Here one must presume an initiation ceremony whose method was used for the legendary sages as well as patients of today. The technique which is called ‘retreat in a hut’ implies the idea of regressus ad uterum. Rejuvenation which constitutes, from the biological point of view, a regeneration of the body (kāyakalpa) must be considered on the symbolical plane as a ‘new birth’: the patient is assimilated to the embryo, and to the uterus correspond both the ‘hut’ described in the classical Āyurvedic treatises and the dark enclosed premises recommended by the modern kavirāj.