This paper describes the technological status of and some challenges in the manufacturing of Cu(In,Ga)Se-2 (CIGS)-based solar cells on flexible polymer and metal substrates. Substrate characteristics such as thermal expansion properties and stability, surface roughness, or substrate composition, strongly influence growth and properties of the following layers. For example, adhesion failure, cracking, or contamination by diffusion of impurities from the substrate may occur with some substrates. Aspects of (external) sodium incorporation into CIGS are discussed for high and low CIGS deposition temperature. Low-temperature deposition processes are particularly important when polyimide substrates are used. The electrical insulation of metal foils by dielectric barriers (e.g. SiOx or Al2O3) allows the fabrication of monolithically integrated modules. A soft and selective patterning technique based on laser scribing and mask-free photolithography is described. Working modules as large as 20 cm x 30 cm were achieved with these methods. (C) 2004 Elsevier Ltd. All rights reserved.