Nonlinear optical single crystals of YCa4O(BO3)(3) (YCOB) with good optical quality were grown from boron-tri-oxide flux for the first time. Polycrystalline YCOB samples were synthesized from the solid-state reaction method. Optimum conditions for the growth of YCOB crystals from the flux were determined. Single crystals of YCOB with dimensions 10 x 5 x 5 mm(3) were obtained by the method of 'slow cooling'. The grown crystals were characterized by XRD, UV-vis-NIR, and Fourier transform infrared (FTIR) studies. The powder XRD pattern reveals the formation of YCOB Compound. The lattice parameters were identified through single crystal XRD Studies. The UV-vis-NIR results show that the crystal has a sharp cutoff at 220nm and is nearly 78% transparent over a wide wavelength range enabling it for applications in the UV region. The functional groups belonging to the YCOB single crystals were identified by the FTIR results. The primary emphasis is laid to describe 'flux technique' as an alternative method to grow YCOB single crystals. The results are presented and discussed. (C) 2008 Elsevier B.V. All rights reserved.