The current industrial PhD work was aimed at synthesising a photocatalytic composite material which could be used to give organic wood paint films self-cleaning and anti-microbial properties. The current PhD work was done in collaboration between Dyrup A/S and Technical University of Denmark. The paint industry constantly faces updated restriction on toxic chemicals as for instance biocides which has prompted the search for alternative strategies for increasing the durability of their products. Photocatalysts are generally known to have adverse effects on organic coatings due to the highly reactive chemical species created by the photocatalytic reaction, which can damage the coating itself. The novel strategy for integrating the photocatalyst into the coating proposed in this work however offers most of the benefits of such self-cleaning coatings without the disadvantages. The thesis consists of an introduction to relevant concepts and literature followed by results, presented as research papers, and a patent application. Four research papers are introduced as individual chapters. Chapter 4 discusses the synthesis and optimisation of anatase TiO2 coated microspheres, chapter 5 discusses the self-cleaning properties and degradation mechanisms of photocatalytic organic coatings containing TiO2 coated microspheres, chapter 6 discusses the rheological and mechanical properties of such coatings and chapter 7 discusses the durability and weather stability of photocatalytic self-cleaning coatings containing TiO2 coated microspheres. The results show that introducing a photocatalyst into an organic paint system as a coating on inert carrier particles results in durable and weather stable paint films. The paint films exhibit selfcleaning properties and are able to resist the attack of micro-organisms. The effect of the photocatalytic reaction on the organic binder is found to be minimal and the films are found to be more durable during outdoor exposure than conventional paint systems. The microspheres only influence the paint viscosity to a small degree and although the mech anical properties are generally degraded by the rigid filler the actual performance is improved by an altered mechanism for crack propagation in the films. The project was funded by Dyrup A/S and the Danish Agency for Science and Innovation.