The linear polarization degree of K-alpha and K-beta X-rays of some elements in the atomic range 57 less than or equal to Z less than or equal to 69 has been measured. In addition, the polarization effect on the intensity ratio of these elements is investigated. It is found that the K-beta X-rays are more polarized than K-alpha X-rays. The polarization effect on the K-beta/K-alpha intensity ratio was investigated. Because the polarization of characteristic K X-ray is not found in the literature the comparison was not made with other experimental and theoretical results. (C) 2001 Elsevier Science B.V. All rights reserved.