The effect of axial stresses on rock is known to affect porosity, permeability, and rock compressibility and will be important in some reservoir rock types that are buried deep and at high temperatures. The aim of this project is to determine reservoir rock properties under in situ stress conditions and to observe the effects of axial stresses on reservoir rocks. For this purpose, a uniaxial stress device, which is capable of applying axial stress to the core samples, was used. The core samples chosen were sandstone, limestone, and barea. The experiments were done by measuring porosity in a helium porosimeter measuring liquid permeability, and measuring maximum load on the core samples. The loading rate was kept constant with increasing stresses up to the breaking point of the specimen. The results obtained are important for reservoir characterizations, reservoir managements, enhanced oil recovery processes, and production applications such as well fracturing.