Öz Compositions of the equ‘diprated solid-liquid phases in the A1-CUA12, Al-Si and Pb-Sn Systems were exam ined by using Cameca microprobe microanalyser. Ali the solid and liquid phases were found to be uniform for the Systems. The m easured consentraticns of the solid and liquid phases in the A1-CU A12 system, the solid phases in the Al-Si system, the solid Pb and the liquid PbSn phases in the Pb-Sn system were in agreem ent w ith the phases diagram values. However the m easured compositions of the solid Sn phase and liquid Al-Si phases were found to be quite different from the phase diagram values. The difference for the solid Sn phase came from the semaring effect. and the liquid AlSi phase m ight came from the very different obsorbsi- tion coefficient for A lK a and S İK a lines. The corrected consantration of th e Iiquid AlSi phase was also in good agreem ent w ith the phase diagram values.