ABSTRACT: In this study, the changes in the index and strength properties of calcarenites, which are widely used as buildingstone in the Turkish Republic of Northern Cyprus, after being subjected to high temperatures between 200 and1000oC, and the effects of high temperatures on microstructure of the calcarenite were investigated by using electronmicroscope images. In order to represent a real fire incident, the samples were heated using the temperature-timecurves recommended by Eurocode, and left to cool at room temperature after 2 hours of exposure at target temperature.After the experimental studies, it was observed that there was no significant change in density and weight loss valuesup to 600 oC. After 600oC, a sudden decrease in density was recorded, at 1000 oC the density dropped below 1 due to microcracks. Likewise, the weight loss value reached 41% depending on the calcination process observed in calcites.P-wave velocity and tensile strength values decreased continuously depending on the temperature. However, thisdecrease became more pronounced after 600 oC and reached the most prominent level after 800 oC. In SEM images,discontinuity formation was observed due to the agglomeration that developed especially after 600 oC. This situationis considered as the main reason for the decrease in strength. In experimental studies applied by Eurocode, it isstated that the temperature of a fire that will occur outside the building will not exceed 680oC, and in a fire that willoccur indoors, the temperature will exceed 1000 oC. For this reason, it is recommended that calcarenites, which arethe subject of the study, are used only as outer coatings in buildings