Objective: Apoptosis of human mast cell line (HMC-1) could be i nduced by tripterine, one of the pure ingredients of tripterygium wilfordii hook . The paper is to explore the cell changes in morphology of apoptotic cells. Methods: On or after exposure to tripterine, cells were observed with microscopy and electromicroscopy. Apoptosis was detected by flowcytometry and T UNEL. Results: Sunflower-like cell (SLC), cell surrounded by formed or forming apoptotic bodies with chromatin condensed or not, were seen in the apoptotic process, which was negtive to trypan blue dye. SLC could occur in 20 minutes after incubated with tripterine and survive for several hours. The f ormation of SLC was at a time- and dose- dependent manner. The results of apop tosis assayed by SLC count were significantly correlated with that mearsured by TUN EL or PI/FCM in first 8 h. The SLC could easily be determined by microscopy in t he condition of culture. The results of SLC counted by inter- or intra-examine r were consistent. Conclusion: The results suggest that SLC is a characteristic morphologic change of apoptotic cells, and can be a good indicat or for HMC-1 cell apoptosis.