The glandular kallikreins are a family of serine proteases thought to be involved in maturation of some growth factors. We have investigated the possibility that members of this family are responsible for cleavage or glycosylation of growth factors produced by cells of hemopoietic or lymphoid origin. Kallikrein mRNA was detected by blot hybridization only in RNA from mesenteric lymph nodes and Peyer's patches. It was not detected in T cells or the T lymphoma cell line EL-4 nor in macrophages or macrophagelike cell lines, even when stimulated to undergo steps in the differentiation pathway. We conclude that genes in the kallikrein cluster do not code for enzymes responsible for processing growth factors in these cell types.