In this paper, a novel optimal watermarking scheme based on singular-value decomposition (SVD) using genetic algorithm (GA) is presented. The singular values (SVs) of the host image are modified by multiple scaling factors to embed the watermark image. Modifications are optimised using GA to obtain the highest possible robustness without losing the transparency. Experimental results show both the significant improvement in transparency and the robustness under attacks. (C) 2007 Elsevier GmbH. All rights reserved.