['To examine the relationship between sperm strict morphology and sperm chromatin integrity.', 'Prospective study.', 'Infertility clinic.', 'Eighty-seven consecutive semen samples from non-azoospermic men presenting for infertility evaluation and 6 samples from fertile donors.', 'Assessment of standard semen parameters and sperm chromatin structure assay (SCSA) parameters (%DFI [DNA fragmentation index] and %HDS [high DNA stainability]). Evaluation of %HDS and %DFI after treatment with dithiothreitol (a thiol-reducing agent used to decondense sperm nuclei) was also undertaken.', 'Relationship between sperm strict morphology defects and SCSA parameters (%DFI and %HDS).', 'We observed significant relationships between the percentage of normal sperm forms and both %HDS (r = -0.40) and sperm motility (r = 0.32). We also found significant relationships between sperm head defects and both %HDS (r = 0.40) and sperm concentration (r = -0.39). Sperm tail, midpiece, and neck defects were not significantly related to the SCSA parameters. Treatment of spermatozoa with dithiothreitol (to induce decondensation) resulted in a substantial increase in %HDS but no measurable change in %DFI.'] Is sperm head morphology related to high deoxyribonucleic acid stainability assessed by sperm chromatin structure assay?