Gradient single crystal fibers of GdTaO4-YbTaO4 have been grown by laser-heated pedestal growth (LHPG). The crystals of the compounds have differences in the lattice parameters of Delta a/a(av) = 2.5%, Delta b/b(av) = 2.2% and Delta c/c(av) = 0.9%. The crystals obtained exhibit an optimum linear distribution of the compounds along the fiber axis and a lattice spacing gradient value of 2.91%/cm for (6 4 0) reflection, the largest value of lattice spacing gradient reported up to this moment. The compositional and structural analysis shows that the LHPG technique and the GdTaO4 YbTaO4 system are very promising for obtaining good quality gradient crystals with large lattice parameters gradient. (c) 2005 Elsevier B.V. All rights reserved.