Single crystals of Gd1-xYxCa4O(BO3)(3) (GdYCOB) were grown by conventional Czochralski technique in various atmospheres (Ar, air, and Ar atmosphere containing 1% oxygen). We examined the effect of the growth atmosphere on the phase-matching properties. GdYCOB grown in air (GdY-air) had smaller birefringence than that grown in Ar atmosphere (GdY-Ar). A similar effect has been confirmed for crystals grown in an Ar atmosphere that contain 1% oxygen (GdY-1%O-2). These results suggest that crystals with fewer oxygen defects have smaller birefringence. (C) 2002 Elsevier Science B.V. All rights reserved.