Results of structural characterization of (AlxGa1-x)2O3 single crystals grown from the melt with Al content x up to 0.04 are presented. Bulk (AlxGa1-x)2O3 crystals were grown by exploring the Czochralski method [1]. Transmission electron microscopy (TEM) was used to investigate defect structure of the material with various composition, X-ray diffractometry was used to measure Al content x, to inspect crystallography of the growth facets and to characterize the structure quality of the samples. Possible types of defects were identified in the samples with various composition including single dislocations, cracks, and low-angle misorientation block boundaries. Measured full-width at half-maximum (FWHM) of rocking curves of 200" confirmed high quality of the grown crystals.