CIBA-GEIGY Corporation wishes to inform the Environmental Protection Agency of certain preliminary information received in a FLASH REPORT entitled TK 12850, 28-Day Study in the Rat. TK 12850 is a test code designation for Irgaform 1266, also known as Dimezone S, which is 4-(hydroxymethyl) -4-methyl-1-phenyl- 3-pyazolidinone, CAS. No. 13047- 13-7. Irgaform 1266 is a phenidone derivative used as a photographic developing agent. He have imported approximately 1,200 lbs. over the past two years, 880 1bs. of which is still in inventory. Three to five major potential customers in the U.S. are already using this chemical substance commercially. Additionally, there are many smaller photographic developing companies which would purchase developer chemicals containing this substance in solution. The total U.S. market for the substance, which has been in use commercially for about 20 years, is about 110,000 1bs.