The structure of morphogen of Dictyostelium discoideum, DIF-1, which was elucidated by Morris et al. proved to be closely similar to that of differanisole A which had been isolated by us from the metabolites of a simple eucaryote, Chaetomium, as the differentiation-inducer of murine and human undifferentiated tumor cells. This fact seemed to suggest the molecular structure playing an important part in differentiation and development beyond species. We have already examined whether differanisole A induces the differentiation in Dictyostelium discoideum, and it was morphologically and biochemically confirmed. In this study, we examined whether DIF-1 induces the differentiation in murine and human leukemia cells. Above the concentration of 2 micrograms/ml (6.5 microM), DIF-1 induced the differentiation in murine erythroleukemia B8 cells and in human leukemia K562 cells into the hemoglobin-synthesizing erythrocyte-like cells.