A reel-to-reel electron beam evaporation system has been developed to continuously deposit Y±BaF 2 ±Cu precursor for ex situ YBa 2 Cu 3 O 7Àx (YBCO) processed ®lms. The quality of a YBCO ®lm on biaxially textured, oxide bu€ered, Ni tape strongly depends on the condition of the precursor deposit. For continuous precursor deposition, a uniform cation stoichiometry (i.e., Y:Ba:Cu ˆ 1:2:3) over the entire length of precursor ®lm is essential. Rutherford backscattering spectrometry studies indicated that the partial pressure of water vapor during the deposition has a signi®cant e€ect on cation deposition rates and the oxygen content in the precursor ®lm. The oxygen content of the precursor is increased and the precursor stability upon exposure to air is improved by introduction of water vapor during precursor depo-sition. High quality precursor ®lms with a thickness of 300 nm have been deposited on lengths of rolling-assisted, biaxially textured substrates in the reel-to-reel electron beam evaporation system. In this paper, long length precursor deposition processing will be discussed. Properties of some post-annealed YBCO ®lms will also be presented. Ó 2001 Elsevier Science B.V. All rights reserved.