According to the phase transformation kinetics that we recorded by dilatometry in rapid cooling of low carbon steel, some amount of isothermal bainite appeared in the middle of martensitic temperature range. Presumably caused by adiabatic heating in the exothermal transformation, such an unexpected effect was confirmed by TEM data on the lath thickness, dislocation density and carbide particles. Furthermore, to assess a volume fraction of the detected bainite, statistics of crystal curvature (orientation gradient) was analyzed in terms of EBSD data. The combined analysis of results obtained using those three techniques suggests that certain amount of lath type bainite is formed not only below the martensite start temperature but also slightly above it.