Reinforced autoclaved aerated concrete (RAAC) panels are widely used in mainland Europe. The experience in the UK has been rather mixed. Some serviceability problems have been encountered with some of the panels that were designed and built before 1980. A new European Standard covering prefabricated RAAC components is about to be published, so it is timely to examine this form of construction.This report does not apply to beam-and-block floors or walls that contain autoclaved aerated concrete (AAC) blocks in their construction, nor to any other AAC components. 22 pages.