Effects of europium substitution on the stoichiometry, structure and superconductivity of the Bi2Sr2CaCu2O 8+y phase have been investigated. Partial replacement by calcium by europium promotes the single-phase formation and leads to an uptake of extra oxygen into the structure. Oxygen content in the Bi2Sr 2Ca1-xEuxCu2O8+y materials was determined by the thermogravimetric hydrogen reduction method. In an attempt to locate the intercalated oxygen atoms, X-ray, neutron and electron diffraction techniques were used. In addition, the samples were characterized by AC magnetic susceptibility measurements as well as by 151Eu Mossbauer spectroscopy. The applicability of these methods and the results obtained thereby are discussed.