A man with globozoospermia was treated in our in-vitro fertilization-intracytoplasmic sperm injection (ICSI) programme. In the treatment cycle, 24 oocytes were collected from his wife. All the oocytes were at metaphase II stage. The semen sample produced on the day had a normal sperm count, good motility, but with 100% globozoospermia. All oocytes were injected with randomly selected spermatozoa and of these, two oocytes showed two pronuclei and another contained a single pronucleus. The remainder were unfertilized. The normally fertilized oocytes (two pronuclear) cleaved to the four-cell stage and were transferred to the patient. At 48 h after ICSI, the 21 unfertilized oocytes were processed for cytogenetic analysis. All oocytes contained a haploid chromosome set. The only abnormality seen was a chromosome fragment in one metaphase. Eighteen oocytes contained decondensed sperm nuclei and of these, 14 nuclei were beginning to show signs of premature chromatin condensation (PCC) and the other four showed strong signs of PCC. Thus it appears that in some forms of globozoospermia, arrest of nuclear decondensation and/or PCC are another cause of fertilization failure. The most likely cause for this is the absence or down-regulation of spermatozoa associated activating factor in round-headed spermatozoa.