AlxGa1-xN/GaN multilayers (x less than or equal to 0.12) deposited on AlN(0001) buffer layer/6H-SiC(0001) substrate combinations have been investigated using high resolution X-ray diffraction. Rocking curves (omega) showed that the AlxGa1-xN layers in the main contained a reduced dislocation density relative to the underlying GaN layers. The line widths of the radial scans (2 theta - omega) of the AlxGa1-xN layers increased as the Al mole fraction increased due to alloy broadening. The in-plane lattice constant (a) of the AlxGa1-xN layer for each sample was equivalent to that of the GaN layer, indicating the layers were coherently strained. The strain in the AlGaN layer was tensile for each sample. This was determined using high-resolution reciprocal space maps of the (015) and (024) planes which revealed that the AlxGa1-xN and GaN lattice points had the same value of the in-plane components of the reciprocal lattice vector ((S) over bar(parallel to)). For higher Al mole fractions, the samples were severely cracked, indicating the strain in the AlxGa1-xN layers exceeded critical values.