A systematic study of L X-ray spectrum has been made on the elements Dy, Ho and Er in the pure form elements and compounds to look into the influence of chemical effect. The vacancies were created by 59.54 key gamma-rays from an Am-241 radioactive source. The L X-ray emission spectra of heavy elements taken with the currently available Si(Li) detectors show four or five distinct peaks. Corrections for sample absorption and spectrometer efficiency were applied to the measured relative intensities. The results show agreement with the theoretical predictions of Scofield (Scofield, 1974a). (C) 2011 Elsevier Ltd. All rights reserved.