['To study the relationship of total levels, localization patterns, and proportions of sperm exhibiting phospholipase C zeta, with fertilization rates after in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).', 'Laboratory study; controls vs. patients after IVF (n = 27) or ICSI (n = 17) treatment.', 'Fertility center.', 'A total of 44 semen samples, subjected to either IVF or ICSI treatment. Oocyte collection, ICSI or IVF, determination of sperm concentration and motility, and immunocytochemical analyses of phospholipase C zeta (PLCζ).', 'None.', 'Percentages of sperm exhibiting PLCζ.', 'Significant positive correlation between ICSI fertilization rates and total levels, localization patterns, and the proportion (percentage) of sperm exhibiting PLCζ. Total levels, localization patterns, and the proportion of sperm exhibiting PLCζ are correlated with fertilization rates for ICSI, but not for IVF.'] Are total levels , localization patterns , and proportions of sperm exhibiting phospholipase C zeta significantly correlated with fertilization rates after intracytoplasmic sperm injection?