The probabilities for vacancy transfer from K to L shell, eta(KL), were obtained by measuring the K-beta/K-alpha intensity ratios in 25 elements over the range 57 <= Z <= 92 using a 25 mCi Co-57 filtered source for excitation. The K X-rays were measured by using a Si(Li) detector. The theoretical values were calculated via the radiative and radiationless transition rates of these elements. The comparison between present experimental results and theoretical predictions showed that both results agreed well. The experimental and theoretical values were fitted against atomic number (Z). The measured values of eta(KL) for Tin, Yb, Lu, Hf and Ir are being reported here for the first time. (c) 2005 Elsevier B.V. All rights reserved.