The aim of the present work was to study the negative lattice expansion of the La(Fe,Si)(13) phase in the LaFe11.2Co0.7Si1.1 alloy modified by Ce, Ho, Pr or Mn. The highest change of lattice constant was observed for sample doped with Ce, which was result of the first order phase transition, previously observed in this alloy. The gradual decrease of relative change of lattice parameter with increase of Mn content was detected. Furthermore, anomalous behavior of temperature dependence of lattice constant for alpha-Fe phase was also observed. The X-ray diffraction analysis showed that this phenomenom is caused by negative lattice expansion of the La(Fe,Si)(13) phase.