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.