A simple, inexpensive apparatus for the production of pure ozone vapor for use in the in situ growth of superconducting oxide thin films is described. Pure condensed ozone is distilled at 77 K from a dilute mixture of ozone in oxygen gas. The condensed ozone is subsequently heated, raising its vapor pressure to provide an adequate flow of ozone gas into the thin film growth chamber. Thin films of YBa2 Cu3 O7-x with zero resistance at temperatures as high as 85 K have been grown with a deposition chamber pressure of only 2×10-7 Torr and without a post-deposition anneal processing step. Unlike most other commonly used forms of highly reactive oxygen, ozone can be made and stored in very pure form. This makes it very useful when a well-characterized oxidizing gas is needed for systematic studies of the growth kinetics and oxidation of the films. Safety aspects of the ozone-production process are discussed.