OBJECTIVE To evaluate the sperm DNA fragmentation index (DFI) and sperm malformation rate (SMR) before intracytoplasmic sperm injection (ICSI) and their impact on the clinical outcome of ICSI. METHODS This study included 79 cycles of ICSI because of oligoasthenozoospermia. We detected the sperm concentration, percentage of progressively motile sperm, DFI and SMR at 3 to 6 months before ICSI, and analyzed the relationship of DFI and SMR with the outcome parameters. RESULTS Of the 79 oligoasthenozoospermia cases, DFI was found to be normal (< or = 25%) in 51 and abnormal (> 25%) in the other 28, significantly increased in the latter (14.18% vs 41.47%), and coincidently, SMR, too, was normal (< or = 96%) in 51 cases and abnormal (> 96%) in 28, significantly higher in the abnormal than in the normal cases (87.88% vs 98.46%). There were no significant differences between the normal and abnormal DFI groups in age, females'BMI, number of oocytes retrieved, and number of embryos transferred, nor between the normal and abnormal SMR groups in the number of fertilized oocytes and quality embryos, biochemical pregnancy, clinical pregnancy, and early pregnancy loss. Sperm DFI was significantly positively correlated with SMR (r = 0.231, P < 0.05). CONCLUSIONS ICSI may reduce the rates of biochemical pregnancy and clinical pregnancy for men with increased sperm DFI (> 25%) and SMR (> 96%) by strict detection criteria, but with no statistically significant difference from normal males. Our findings need to be supported by further studies with larger sample sizes.