Callotasis is a new technique of limb lengthening involving slow dis-traction of the callus formed in response to a diaph_ysea! corticot-omy or submetaphyseal Corticotomy, uniaxial external fixator allows gradual distraction of 1.5 mm/day at the corticotomy site. The distraction begins qfter 2 weeks from the corticotomuy. When the required length is attained the fixator is held in a rigid rnode until a considerable radiologic evidence of callus is observed. me fixator is then removed and a well molded cast is applied. Twintyfour bony segrnents had been lengthened in twinty two patients. The age ranged from 8 to 22 years with a mean age 16.6 years. The shortening rangedfrom 4 to 16 cm with an average 7,95 cm. Good ra-diological and functional results were obtained. The coz-apucations of this method were reported and discussed