The L X-ray fluorescence cross sections (σ Ll , σ Lα , σ Lη , σ Lβ , σ Lβ6 , σ Lβ2 , 4 , σ Lβ1 , 3 , σ Lβ9,10 , σ Lγ , σ Lγ1 , σ Lγ2,3 , σ Lγ4 and σ Lγ5 ) and relative intensities (I Lα , I Ll , I Lη , I Lβ , I Lβ6 , I Lβ2,4 , I Lβ1,3 , I Lβ9,10 , I Lγ , I Lγ1 , I Lγ2,3 , I Lγ4 and I Lγ5 ) for some elements in the atomic range 78≤Z≤92 have been measured at 59.54keV photons energies from an Am-241 point source. The L X-rays emitted by samples have been counted by a Si(Li) detector. The L X-ray fluorescence cross sections and relative intensities have been also calculated theoretically by using atomic parameters. The measured values have been compared with the theoretical values.