AIM: To study effects of chebulinic acid on erythroid and megakaryocytic differentiation in K562 cells. METHODS:The benzidine staining method was used to evaluate hemoglobin synthesis; the expression of erythroid specific glycophorin A (GPA) protein and megakaryocytic surface marker CD61 was determined by flow cytometry using fluorescence labeled antibodies; erythroid and megakaryocytic mRNA expression was analyzed by RT-PCR.RESULTS: During erythroid differentiation induced by butyric acid (BA) or hemin, chebulinic acid not only inhibited the hemoglobin synthesis of BA- and hemin-treated K562 cells in concentration-dependant manner with IC50 of 4 μmol/L and 40 μmol/L respectively, but also inhibited another erythroid differentiation marker acetylcholinesterase at the concentration of 50 μmol/L in the cells either treated or untreated with each erythroid differentiation inducers,whereas chebulinic acid 50 μmol/L did not change GPA protein expression in these cells significantly. When K562 cells were treated with TPA 50 μg/L for 72 h to induce megakaryocytic differentiation, the presence of chebulinic acid 50 μmol/L slightly provoked the decrease of GPA protein expression induced by TPA. Chebulinic acid did not change the TPA-induced CD61 expression at the same concentration. Chebulinic acid also reduced the mRNA levels of erythroid relative genes including γ-globin, PBGD, NF-E2, and GATA-1 genes in K562 cells either treated or untreated with BA, whereas chebulinic acid upregulated the mRNA levels of GATA-2 transcription factor in these cells. CONCLUSION: Chebulinic acid had inhibitory effect on erythroid differentiation likely through changing transcriptional activation of differentiation relative genes, which suggests that chebulinic acid or other tannins might influence the efficiency of some anti-tumor drugs-induced differentiation or the hematopoiesis processes.