We have investigated the effect of aluminum incorporation on the structure and superconducting transition temperature of single crystals of high-Tc cuprate perovskite superconductors. The use of alumina crucibles for crystal growth results in incorporation of aluminum to varying extents in crystals of composition Ba2YCu3-xAlxO7, x=0-0.22. We have performed x-ray studies on several crystals to determine structural effects of Al incorporation. We find that aluminum substitutes only for copper atoms in the chains. Superconducting transition temperatures Tc determined by dc diamagnetic susceptibility measurements change only slightly, to 80 K for x=0.1, then drop sharply with higher aluminum concentrations. Results are discussed in relation to the importance of the Cu-O chains and oxygen stoichiometry to superconductivity in Ba2YCu3O7.