A method of forming a black-and-white image of very high contrast having a gamma value of 8 or above is disclosed, using a negative imagewise exposed photo­sensitive material comprising a support having thereon at least one hydrophilic colloid layer, at least one layer which is a silver halide emulsion layer, at least one of said hydrophilic colloid layer containing a hydrazine derivative represented by formula (I), comprising processing the photosensitive material with a developer having a pH of 11.2 or lower, said developer being substantially free from benzotriazoles to thereby provide a wide exposure latitude and steady image formability:
wherein R₁ represents an aliphatic group or an aromatic group; R₂ represents a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, a carbamoyl group or an oxycarbonyl group; G₁ represents a carbonyl group, a sulfonyl group, a sulfoxy group,
or an iminomethylene group; and each of A₁ and A₂ represents a hydrogen atom, or one of A₁ and A₂ is a hydrogen atom and the other is an alkylsulfonyl group, an arylsulfonyl group, or an acyl group.