L, subshell fluorescence yields w 1 of Pt and Hg have been determined by comparing the intensities of K and L X-ray spectra emitted after the disintegration of 1 9 5 A ~ and 1 9 9 A ~, respectively. For Pt w 1 was also obtained by measurement of the L, X-ray photons emitted per disintegration. A value of the Coster Kronig f,, yield of platinum was also obtained.The experimental results are: