Thrombocytopenia is a common hemostatic abnormality in the newborn infant. The early diagnosis of thrombocytopenia and the underlying primary pathology process play an important role in reducing the risk of severe complications and mortality. We performed a 2-year prospective study of 643 neonates admitted to our neonatology unit to determine the frequency, predisposing factors, and clinical impact of thrombocytopenia. Thrombocytopenia developed in 18.2% of the preterm neonates and 0.8% of the term neonates. Prematurity, sepsis, hypoxia, intrauterine growth retardation, and disseminated intravascular coagulation were identified as predisposing factors for thrombocytopenia. The incidence of complications and mortality were higher in thrombocytopenic infants. Especially the prognosis was worse in cases who had mucosal hemorrhage, without a relation with the degree of thrombocytopenia. The thrombocytopenia occurred by day 2 in 43% of the infants, and resolved by day 8 in 61%. The platelet count nadir occurred by day 2. Since thrombocytopenic infants are at greater risk for bleeding, and the thrombocytopenia itself may have contributed to the high mortality, predisposing factors such as prematurity, infections, hypoxia must be eliminated by prividing better care, giving adequate hygiene of both mother and the baby during the prenatal, natal, and neonatal period. © 1994 Dr. K C Chaudhuri Foundation.