The precalcination of several limestones is investigated as a pre-activation method for combustion calcium looping systems. The temperature and time of precalcination varied between 1050 and 1100 degrees C and 10-60 min, within the range of those proposed in recent papers on the subject. After the precalcination, the sorbents were subjected to standard carbonation/calcination cycles in a thermogravimetric analyzer to check for any improvement in sorbent stability after the initial drop in CO2 carrying capacity, as a result of the precalcination step. In contrast to what has been reported by other authors, there was no sign of sorbent improvement that could be linked to the precalcination step. The use of a short carbonation time in our cycling experiments, resembling those expected in large scale combustion Ca-looping systems, seems to be the main cause to explain our discrepancies with other authors. A model previously used for other applications provided a reasonable interpretation of the observed trends during the precalcination step and subsequent carbonation-calcination cycles.