The lectin-binding pattern of malignant and benign human epidermal tumours was studied. Twelve squamous cell carcinomas and ten kerato-acanthomas were investigated, using fluorochrome-conjugated lectins. Lectins used were Canavalia ensiformis agglutinin (Con-A), Helix pomatia agglutinin (HPA), Phaseolus vulgaris agglutinin (PHA-L), and Ricinus communis agglutinin (RCA-120). Two types of fluorescence pattern, Intercellular 'Pemphigus-like' and Peritumoral, were noted. Both allowed classification of these tumours on the basis of their lectin-binding reactivity. Moreover, the expression of receptors for these lectins made it possible to distinguish between low-grade and well-differentiated squamous cell carcinomas.