AbstractEstrone,6‐7‐3H in benzene has been found to exhibit greater decomposition when stored at −5 °C than when stored at +5 °C. The reason is attributed to lack of uniform dispersal of the solute due to solvent crystallization. The non‐distillable residues from commercial solvents have been found to cause rapid destruction of a stored radiochemical if not removed before storage. Data is presented which indicates that the best method for reducing the total amount of decomposition of labeled steroids which are stored for extended periods of time is repurification at regular time