Abstract The mechanisms of the photochemical reactions of triphenylgermane and 1- naphthylpitenylmethylgermane in solution were studied, by measurement of the transient absorption spectra of their triplet states and germyl radicals. The rate constant for the chlorine abstraction reaction by each radical with CCl 4 was determined to be (6.6±1.0)× 10 8 s− 1 mol− 1 dm 3 at 28.5 C.