The spectrum of alternatively spliced IL-4 and IL-6 gene mRNA was studied in peripheral blood mononuclears from healthy donors and in human fetal tissues. It was found that the expression of alternatively spliced IL-4 and IL-6 gene mRNA in fetal tissues is tissue specific and that hemopoiesis- and immunopoiesis-related tissues differ by the amount of IL-4 and IL-4δ2 mRNA. An mRNA variant IL-4alt3 carrying partial exon 3 deletion was for the first time identified in human mononuclear cells.