We demonstrate combinatorial approach in investigation of organic thin film fabrication. "Combinatorial substrate screening", which is the deposition onto several kinds of substrates simultaneously, is useful to choose suitable substrate for organic thin film growth. "Combinatorial thickness-gradient films" can be fabricated using a moving mask which travels from an edge to another edge of substrate continuously during the deposition. The combinatorial thickness-gradient film can be regarded as the library for time evolution of film growth during the deposition. This mapping can serve as a powerful method for the research of growth of thin film in an initial stage. Besides, combinatorial thickness-gradient film can be utilized for the examination of a buffer layer effect. These techniques enable us to quickly optimize for the fabrication of high-quality organic thin films. (c) 2005 Elsevier B.V. All rights reserved.