We present the experimental results of the AC susceptibility of YBaCuO. Presence of magnetic hysteretic features is analyzed and ascribed to granular nature of YBaCuO. We discuss the necessity of treating the high-temperature superconductor as a granular-like system with grains embedded in a weakly superconducting host. 1. Introduction Bulk-sized high-temperature superconductors are possible candidates for various applications, like magnetic bearings or flywheels, strong electromagnets or quasi-permanent magnets, etc. However, structural defects (cracks, grain boundaries) can act as weak links that reduce substantially the current- carrying capability and cause inhomogeneous distribution of magnetic flux density. The latter leads to degradation of levitation force or rotation speed of flywheels, etc. Thus, study of the role of weak links, and the interaction of magnetic vortices with pinning centers and the weak link system is of crucial importance for developing the suitable material for practical applications. The AC susceptibility measurement is a useful tool for investigation of magnetic properties of high- temperature superconductors. Important parameters, like the critical temperature Tc, the critical current density jc and its dependence on temperature or magnetic field, the pinning constant, the irreversibility line, etc., can be derived using this method. However, complicated spatial distribution of magnetic flux density within the samples yields problems in interpretation of experimental data, and the method thus ceases to give a straightforward picture of the material measured. Therefore, serious corrections, based on realistic theoretical models, have to be introduced into evaluation of experimental results. In this paper we concentrate on hysteresis of the AC susceptibility with respect to applied DC magnetic field. We analyze experimental results from the point of view of necessity of corrections in the parameter calculations, due to granular-like behavior of the samples. The sample investigated is a bulk YBaCuO sample. Due to its polycrystalline nature, it demonstrates well the granular-like behavior and its impact on AC susceptibility experiment. It is necessary to accent, however, that similar behavior may be present also in textured samples.