Steel contains 0.055%C was intermediately annealed at 780, 825 and 870 degrees C for 60 minutes followed by water quenching to obtain different microstructures. The effect of heat treatment on the microstructure, crystal structure and electric resistivity of heat treated steels were investigated. It was found that the resulting microstructures had ferrite-plus-martensite known as dual phase steels. The volume fraction of martensite increased with growing annealed temperatures. X-ray diffraction analysis showed that dual phase steel microstructures had body cubic tetragonal martensite crystal structures. The individual diffracting planes of body cubic tetragonal martensite were found as (110) (200) and (211). The lowest resistivity (about 8.48 x 10(-8) Omega.m) was obtained for the dual phase steel samples heal. treated at 780 degrees C. Scanning electron microscopy studies were also discussed for dual phase steel microstructures.