Platelet volume measurements have been used to differentiate consumptive and hypoplastic thrombocytopenia. Since thrombocytopenia is a frequent complication of neonatal sepsis, the authors explored the utility of correlating mean platelet volume (MVP) and platelet distribution width (PDW) with bacteremia. In a sample of 156 infants, there was a significantly increased presence of bacteremia in those infants with MPV greater than 10.8 fL and/or PDW greater than 19.1%. High MPV and PDW showed high specificity for detecting bacteremia (95% and 79%, respectively), and had good negative predictive value. Neonates with blood cultures positive at birth (early infection) tended to have normal platelet volumes, while those infected after three days of age (late infection) had dramatic increases in MPV and PDW. Changes in MPV and PDW should be noted when the diagnosis of late sepsis is considered.