The details of Tm3+-doped NaGd(WO4)(2) single-crystal growth are discussed, the results of precise investigations of its structural and spectroscopic characteristics, as well as the analysis of cross-relaxation process of Tm3+ ions (H-3(4)-> F-3(4), H-3(6)-> F-3(4)) in this crystal are presented. Based on the Judd-Ofelt theory, three intensity parameters, spontaneous emission probabilities, fluorescence branching ratios and fluorescence quantum efficiency from H-3(4) and F-3(4) levels were refined. (C) 2009 Elsevier B.V. All rights reserved.