Nd doped Y0.8 Ca0.2 Ba2-x Ndx Cu3 Oy YBNCO compounds with x≤.50 have been prepared by the solid state reaction technique. The structure and the superconductivity for YBNCO compounds are characterized. The zero resistance transition temperature T for each sample was measured. T increases with the increase of the content of Nd in YBNCO as xF0. 15, c0 c0 and decreases as xG0.20. X-ray diffraction studies show that there is no structural phase transition in the whole doping range. The dependencies of the lattice constants and some other structural parameters on the content of Nd for the samples YBNCO with xF0.20 have different behaviour than that for the samples with xG0.25. It seems that the uperconductivity of YBNCO is related to the structural changes due to Ca and Nd co-doping. q1999 Published by Elsevier Science B. V. All rights reserved.