OBJECTIVE: To study the relationship between apoptosis and glomerulosclerosis by establishing an experimental animal model of glomerulosclerosis. METHODS: The rat model of glomerulosclerosis was established by left nephrectomy and intravenous injection of Daunomycin (model group, n=30). The other 30 rats (control group) were injected with normal saline at the same time as the model group. Apoptosis was assayed by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) in the two groups. RESULTS: ① The features of renal histopathology of the model group rats was resembled primary focal segmental glomerulosclerosis in human. ② No significant apoptosis was noted within two weeks in either the control group or the model group. The phenomenon of apoptosis initiated at 4th week. The level of apoptosis in the model group was significantly higher than that in the control group [( 5.4 ± 1.2 ) vs ( 1.6 ± 0.8 )] (P< 0.01 ) at 4th week. The number of apoptotic cells reached the highest level at 6th and 8th weeks ( 8.6 ± 2.8 and 10.1 ± 1.9 , respectively) compared with the control group ( 1.8 ± 0.8 , 1.7 ± 0.5 , respectively) (P< 0.01 ). ③ The total number of apoptotic cells was negatively correlated to the number of glomerular cells from 4th to 8th weeks (r= -0.85 , P< 0.01 ); however, there was a positive correlation between them after 8 weeks (r= 0.91 , P< 0.01 ) in the model group. CONCLUSIONS:  There is a significant correlation between apoptosis and glomerulosclerosis. Apoptosis might play an important role in decreasing glomerular resident cells.