Morphometry was carried out on H&E stained paraffin sections of 29 cases of contact dermatitis (CD) and 35 cases of mycosis fungoides (MF) (patch stage 12; plaque stage 11; tumor stage 12); 9 nuclear parameters, mean thickness of the infiltrate and 5 stereological parameters were assessed for each slide. Application of a non‐parametric discriminant analysis (k‐nearest neighbour method) which is based on median of nuclear areas, mean maximal nuclear diameter, volume density and numerical density of nuclei provided discrimination between CD and patch stage MF at an efficiency of 82.9% (specifity 86.7%, sensitivity 61.5%). Efficiency of discrimination between CD and plaque stage was 92.5% (specifity 89.7%, sensitivity 91.7%) and between CD and tumor stage 100% when discriminant analysis was based on the mean thickness of the infiltrate. Although unequivocal discrimination between CD and MF cannot be achieved in each individual case, morphometry on routine paraffin material obviously provides additional objective criteria for the diagnosis of early