2869 20160701171712.0 10.1017/S1743921310002498 DOI ASTROimport-1026 Marigo, P. 2010 TP-AGB stars in population synthesis models In spite of its relevance, the Thermally Pulsing Asymptotic Giant Branch (TP-AGB) phase is one of the most uncertain phases of stellar evolution, and a major source of disagreement between the results of different population synthesis models of galaxies. I will briefly review the existing literature on the subject, and recall the basic prescriptions that have been used to fix the contribution of TP-AGB stars to the integrated light of stellar populations. The simplicity of these prescriptions greatly contrasts with the richness of details provided by present-day databases of AGB stars in the Magellanic Clouds, which are now being extended to other nearby galaxies. I will present the first results of an ongoing study aimed at simulating photometry, chemistry, pulsation, mass loss, dust properties of AGB star populations in resolved and un-resolved galaxies. We test our predictions against observations from various surveys of the Magellanic Clouds (DENIS, 2MASS, OGLE, MACHO, Spitzer, and AKARI). I will discuss the implications and outline the plan of future developments. Girardi, L. Bressan, A. Aringer, B. Gullieuszik, M. Held, E. V. Groenewegen, M. A. T. Silva, L. Granato, G. L. Stellar Populations - Planning for the Next Decade 262 2010 36-43 http://esoads.eso.org/abs/2010IAUS..262...36M published in NONREF