Objective: To investigate how moderate and/or high levels of DNA fragmentation (DFI), as measured by the sperm chromatin structure assay (SCSA), affect either IVF or IVF with intracytoplasinic sperm injection (ICSI) fertilization, cleavage, blastulation, implantation, and pregnancy. Design: Retrospective clinical study. Setting: Academic human reproduction laboratory. Patient(s): Eighty-nine couples undergoing IVF with conventional fertilization or ICSI. Intervention(s): Sperm chromatin structure assay testing (SCSA) of semen aliquot taken from ejaculate used for assisted reproductive technology (ART). Main Outcome Measure(s): Related DFI to conventional semen parameters and cycle-specific outcomes after ART. Result(s): No patients achieved clinical pregnancy if SCSA values exceeded the DFI (27%, P<.01), moderate DFI (15%, P<.01), or high DFI (15%, P<.05) thresholds. Dividing the DFI sperm population into moderate-fragmentation and high-fragmentation categories did not improve the prognostic value of the SCSA. No coefficient of determination (r(2)) between SCSA parameters and conventional parameters exceeded 0.29. Conclusion(s): Sperm chromatin structure assay identified thresholds for negative pregnancy outcome after ART not identified using conventional semen parameters. This is the first study analyzing the clinical value of sperm DFI to [1] include a large number of ART patients (n = 89), [2] perform SCSA analysis on a semen aliquot from the ejaculate used for ART, and [3] examine how the extent (moderate and high DFT) of DFI influenced ART outcomes. (C)2003 by American Society for Reproductive Medicine.