Operational data for the separation of oxygen isotopes are given on flow rates, concentrations and concentration profiles of the isotope separation plant of the Weizmann Institute of Science which has reached steady‐state operational conditions with regard to the rare and more difficult to separate oxygen‐17 isotope. This plant consists of two sections, namely packed distillation columns and thermal diffusion columns. Data on the columns and packing characteristics are given. The concentrations reached in the distillation section are up to 98% of oxygen‐18 and up to 20% of oxygen‐17. In the thermal diffusion section, concentrations of oxygen‐18 up to 99.9% and of oxygen‐17 up to 96% have been attained.