A review of 392 cycles of in-vitro fertilization (IVF) was carried out in order to identify whether any factors such as sperm concentration at insemination, sperm motility or morphology, oocyte grading, number of oocytes retrieved, patient age, follicular stimulation protocols or duration of follicular growth, could be associated with the incidence of polyploidy or completely failed fertilization. The majority of polypronuclear fertilizations occurred in mature oocytes and in patients < 37 years of age and the incidence of polyploidy was strongly associated with fertilization and pregnancy rates. Fertilization rates were highest with mature oocytes. A significant linear trend was observed with failed fertilization and sperm concentration, morphology and motility. High rates of failed fertilization were found in patients > 37 years of age and with one to five oocytes retrieved. No significant difference was seen in stimulation protocols and oocyte grading between oocytes that fertilized and those that did not. Cycles with good sperm morphology and motility, the presence of mature oocytes, the retrieval of a large number of oocytes and younger maternal age seem to provide the best chance for IVF success.