All-ceramic materials are used because of their good esthetics and biocompatibility. High mechanical strength makes zirconia a suitable material for fixed partial dentures in posterior regions. Most of the common zirconia systems offer white opake frames and so the esthetic advantage of an all ceramic restoration is decreased. The LAVA-system (3M-Espe/Seefeld Germany) which is milling presintered zirconia colours the frames before sintering and gets colours very close to natural dentin. Dental technicians use this colouring solution also for other systems milling presinterd zirconia. The Cercon smart ceramics-system (DeguDent, Hanau/Germany) offers presintered coloured zirconia blanks to advance the esthetics. Objectives: This study examined the influence of the colouring solutions on the flexural strength of zirconia. Another major point is the aging of coloured and white zirconia which is also analysed. Methods: There were 60 round samples of presintered zirconia which were distributed the following way. 20 white samples were prepared according to the manufacturer, 20 coloured by LAVA-frameshade solution, 20 precoloured samples whereof 10 in each case were artificially aged over a fictive period of 5 years. All samples fulfilled the requirements of the standard EN ISO 6782, this experimental setup makes it possible to calculate the flexural strength out of the failure force. Results: The best performance before aging did the white zirconia with an average flexural strength off 1320 MPa, the best aged zirconia is the precoloured zirconia showing 1184 MPa. Its also remarkable that the coloured zirconia loses almost no flexural strength after artiflicial aging. The Weibul module is also increased by colouring the zirconia framework. Conclusion: Coloured zirconia-frames should be used because the reliability and the flexural strength after artificial aging are significantelly better than white zirconia frames. Their better performance may underlie in tighter mesh structure because the metal oxide frameshade is between the zirconia molecules.