Photochemical reactions of substituted tris(trimethylgermyl)germanes I-III in cyclohexane has been studied by steady-state and matrix isolation techniques. Photolysis of trigermanes I-III involved both extrusion of (trimethylgermyl) germylenes and formation of germyl radicals via homolytic fission of germanium-germanium bond. The reaction of trigermanes I-III with CHCl3 and 2,3-dimethyl-1,3-butadiene as trapping agents gave the corresponding 1-germacyclopent-3-enes. The UV absorption bands of germylenes in matrix at 77 K were also observed. A possible suitable mechanism has been suggested to account for the identified products.