The expression of the proto-oncogene c-myc was studied in tumorous skin lesions of (cutaneous) lymphoproliferative diseases (3 cases of pseudolymphoma, 8 cases of non-Hodgkin lymphoma and 1 case of lymph node involvement in mycosis fungoides) in a total of 12 patients. c-myc mRNA levels were quantified by Northern blot analysis followed by densitometric evaluation of the specific bands. Higher levels of c-myc mRNA expression were observed in lymphomas as compared with pseudolymphomas (p greater than 0.05). No significant differences in c-myc mRNA values were detected between B and T cell pseudolymphomas. Our results suggest that c-myc mRNA overexpression is associated with malignant lymphomas of the skin. We conclude that the measurement of c-myc mRNA levels may contribute to further characterize cutaneous lymphoproliferative diseases.