[en] It has been suggested that low molecular weight RNA may play a role in eukaryotic gene regulation. The low molecular weight RNA was electrophoresed on 16% acrylamide gels but very small molecular weight RNA (vsRNA) was not visible after methylene blue staining. Radioautography of 3T3 and HeLa RNA labeled with ³²P demonstrated RNA smaller than t-RNA in size. We subsequently developed a highly sensitive silver staining procedure which revealed a very fine bands of RNA migrating faster than t-RNA. The success of platinum containing antitumor agents has stimulated interest in iridium containing agents. Irradiation of a solution of (NH₄)₂(IrCl₆) in ammonia with UV light for seven hours produced a product active against Ehrlich ascites tumor with a T/C of 140% using a daily dose of 100 mg/kg for 8 days. Testing against L1210 (BDF₁ mice) indicated a low activity with a maximum increase in lifespan of 20%