Three-dimensional atom probe method (3DAP) coupled with field ion microscopy (FIM) was used to study the nano-scale boron segregation to dislocation in B2-ordered FeAl (40 at.% Al). A boron-rich Cottrell atmosphere near an edge \textless100\textgreater dislocation was imaged with atomic resolution and its chemical composition was analysed at local scale. Some macroscopic effects of boron segregation to crystal defects, which are related to the segregation phenomena, are also discussed. \textcopyright 2001 Elsevier Science B.V. All rights reserved.