The mechanical characterization of existing masonry is a difficult task due to the heterogeneous and composite character of the material. In most cases, the historical structure cannot be damaged during the in-situ sampling procedure due to its cultural, historical and economical value. Non-destructive testing techniques have been proposed to minimise the damage during the inspection. Another possibility is the extraction of small samples to be subjected to destructive testing in laboratory. This paper presents the results of an experimental program aimed at calibrating a non-standard testing method for the determination of the mechanical response of existing masonry. Cores of 150 mm diameter were extracted from a masonry wall built in the laboratory. The upper and lower portions of the cylinder were properly regularized to create two plane paral-lel surfaces. The specimen was tested under compression. The results are discussed and compared with those derived from conventional compression tests on stack prisms, built with the same materials. The outcomes of the research show that the test provides an estimation of the compressive strength of the composite material, comparable with that obtained through the standard method. The proposed experimental technique can be helpful for the inspection and the analysis of structures of the built cultural heritage.