Abstract: Recently it has been shown in our laboratory that some estrogens have significant radioprotective activity in dogs, but all of these compounds exhibit serious undesirable side effects especially on sexual functions. In the present paper the relationship between radioprotection and estrogenic activity of a series of compounds with structures related to synthetic nonsteroidal estrogens such as stilbestrol, vallestril, triaryl substituted acrylonitrile etc. was reported in order to obtain radioprotective agents free from estrogenic action, preliminary pharmacological examination gave the following results:1. Most compounds (46 out of 80) possess significant radioprotective action and have good reproducibility.2. The effective doses of active compounds vary in a wide range.3. Some active compounds exhibit radioprotective action when a definite dose is given in different intervals before or after irradiation.4. No parallelism has been found in radioprotective and estrogenic activities.