For some time there has been the need to bring ne, technologies utilising daylight in buildings and to assess their performance for the benefit of those concerned with the building industry, particularly building design practitioners, lighting engineers, builders, product manufacturers, building owners and property managers. As there are many different systems with different purposes and abilities on the market, it is difficult to find the right one. An overview with division into main principles. illustrating sketches and short descriptions of the elements helps a lot to choose the right daylighting system for given conditions. More detailed descriptions can be found in the source book of IEA Task 21. (C) 2002 Elsevier Science Ltd. All rights reserved.