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In this work, the macro and microsegregation of Cr, Si and Mn have been investigated in a high-carbon high-silicon cast steel using X-ray fluorescence (XRF) and electron probe microanalysis (EPMA), respectively. Two different keel block sizes with leg thicknesses of 12.5 and 75 mm have been compared. In each of the keel blocks, three different locations along the leg thickness have been analyzed: A) zone near surface (≈1 mm); C) the central zone of the leg thickness and B) an equidistant zone from A and C. After comparing the analysis performed by XRF in these three zones no macrosegregation of the Cr, Mn and Si has been observed in any of the two keel blocks. However, clear microsegregation patterns have been obtained by EPMA for these three elements; interdendritic zones are enriched while dendrites are impoverished in these elements implying that their partition coefficient is lower that the unity (k < 1). This coefficient has been estimated using the EPMA measurements and Thermo-Calc calculations, finding good agreement between both approaches for Si and Mn but not for Cr. Finally, for both keel block leg thicknesses, similar microsegregation intensity, measured in terms of alloying element concentration has been observed. This result suggests that the cast part size (or dimension) do not have a strong influence on the microsegregation profiles. This it attributed to the back diffusion phenomena involving redistribution of solute during the solidification process., This work has been supported by CONICET, ANPCyT and MINCyT of Argentine [Project PICT 12-1146]. Some of the authors (ITC, DSM, FGC) also acknowledge financial support from the Ministerio de Economia y Competitividad (MINECO) in the form of a Coordinate Project (MAT2016-80875-C3-1-R) and to the Comunidad de Madrid through DIMMAT-CM_S2013/MIT-2775 project. Authors are also grateful to Dr. José Antonio Jiménez for the experimental support with the X-ray fluorescence analysis, the Phase Transformations and Microscopy labs from CENIM-CSIC, and the ICTS Centro Nacional de Microscopía Electrónica (CNME) located at the Complutense University of Madrid, for the provision of laboratory facilities (EMPA) and technical support. ITC is also grateful for financial support of the fellowship 2016-T2/IND-1693, from the Programme Atracción de talento investigador (Consejería de Educación, Juventud y Deporte, Comunidad de Madrid).