The structural morphol. of YBa2Cu3O7-x (YBCO) was investigated by application of the periodic bond chain (PBC) theory. For x = 1, the F forms are {001}, {011}, {013}, {112} and {114}. Attachment energies were calcd. in a broken bond model and in an electrostatic point charge model. For x = 1 the theor. growth habit is tabular to platy {001} with {011} as side faces. For x = 0 {010} also becomes an F form. The habit is isometric with large {001} and {011} and small {010} faces. The outermost layer of {001} contains half of the Cu+ (x = 1) or Cu3+ and O2- (x = 0) ions in an ordered arrangement based on a c(2 * 2) quadratic lattice. For the outermost layer of (010) (x = 0) an ordering scheme of the Cu and O ions is proposed. The occurrence of {010} rather than {011} on grown crystals has to be ascribed to external factors.