The present invention provides a black and white photothermographic material having, on at least one side of a support, an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, and a binder, as well as an image forming method. The black and white photothermographic material is characterized in that 50% or more of a total projected area of the photosensitive silver halide is occupied by tabular grains having a (111) face as a major face; the tabular grains have at least 2 parallel twin crystal planes in a grain; and a variation coefficient of a distribution of distances between closest twin crystal planes is 20% or less. Also provided is an image forming method that includes image exposure using fluorescent intensifying screens and thermal development.