The investigation of the radioactive xenons growing out from radioactive iodines following uranium or thorium fission is summarized in this paper. Two complete chains have been established and identified with their mass numbers. They are: 51Sb133 10 min.-->52Te133 60 min.-->53I133 22 hrs.-->54Xe133 5 days-->55Cs133 and 54Xe135*↗53I135 6.6 hrs. ↓10 min.↘ 54Xe135 9.4 hr. 55Cs135?