A micro-pulling-down process employing Ir crucibles and RF heating has been used to grow single crystal fibers of Yb-doped Y3Al5O12 garnet (YAG). Single crystals ranging up to 550 mm in length have been produced. The fibers were about 1 mm in diameter and were seeded-grown in the <111> direction. Results of X-ray rocking curve measurements and transmittance data were used to discuss the crystalline perfection of the fibers. The effective segregation coefficient of Yb3+ in the process described is reported to be slightly less than 1.0 at a growth rate of about 5 mm/min. (C) 2000 Elsevier Science Ltd. All rights reserved.