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During the restoration works of the Sant'Agata La Vetere church in Catania, a campaign of archaelogical excavations was conducted in order to study the complex site around the religious building. According to tradition and to historical sources, the site was very interesting because a part of the church, in particular the crypt, was built incorporating an apse of the roman praetorium palace. Starting from this assumption, the present study is focused on the resolution of the chronological question about the different construction phases of the crypt. In agreement with archaeologists and architects, samples of bricks are collected in specific area. The ThermoLuminescence (TL) methodology was applied performing measurements on polymineral fine grain phases extracted from each brick. The Equivalent Dose (ED) values were evaluated from TL signals through Added Dose procedure. The annual Dose Rate (DR) was calculated using the radioactive content of samples estimated by ICP-MS analysis and environmental and cosmic dose rates obtained by in situ gamma measurements. From the obtained ages, three phases of construction were individuated: 3rd, 7th-8th and 17th centuries. In particular, the first one could be correspond with the end of the roman period, and it seems to confirm the archaeological hypothesis based on the historical sources. From a methodological point of view, the archaeological issue contributed to study the behaviour vs time of the alpha efficiency coefficient k. The results showed that the value obtained after 30 days has to be considered. [ABSTRACT FROM AUTHOR]