Large erbium calcium oxyborate ErCa4O(BO3)(3) (ErCOB) crystals with high optical quality have been grown by Czochralski method. X-ray powder diffraction experiments show that the crystal has the same structure as that of YCa4O(BO3)(3) and its unit cell constants have been calculated to be a = 0.8095(3) nm, b = 1.6023(5) nm, and c = 0.3562(2) nm with an angle beta = 101.23degrees. When the Judd-Ofelt (JO) theory of parity-forbidden electric-dipole transitions of rare earth ions on non-centrosymmetric sites is applied to ErCOB, it results in a good fit. The experiments show that the radiation transition with green light at 554nm and ultraviolet light at 410nm is likely to provide some practical applications for ErCOB as a laser material. (C) 2002 Elsevier Science B.V. All rights reserved.