1. Bis(phenyldimethylsilyl)mercury was synthesized, the reactions of which with molecular oxygen, benzoyl peroxide, 1,2-dibromoethane, HgCl2, and acetic acid proceed with cleavage of the Si-Hg-Si fragment. 2. A study was made of the photodecomposition reactions of bis(phenyldimethylsilyl)mercury in either benzene or cyclohexane medium at 40 and 80°, and also its thermal decomposition in cyclohexane at 200°. 3. The photoreaction of bis(phenyldimethylsilyl)mercury in triethylgermane solution gives mercury, phenyldimethylsilane, and hexaethyldigermane.