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: ##STR1## wherein R.sub.1 represents an aliphatic group or an aromatic group; R.sub.2 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; G.sub.1 represents a carbonyl group, a sulfonyl group, a sulfoxy group, ##STR2## or an iminomethylene group; and each of A.sub.1 and A.sub.2 represents a hydrogen atom, or one of A.sub.1 and A.sub.2 is a hydrogen atom and the other is an alkylsulfonyl group, an arylsulfonyl group, or an acyl group.