NEONATAL jaundice( physiological jaundice), an extremely …….common occurrence among neonates in the first week of life, can represent a benign physiological process or be the harbinger of serious illness with associated severe neurotoxicity. In the present work, a group of sixty five infants (GpI: control group, GpII: jaundiced neonates, GpIII: Glucose 6 phosphate dehydrogenase (G-6-PD) deficient neonates and GpIV: is the Crigler –Najjar I (CNI) and Crigler –Najjar II (CNII) neonates), were included.The rheological and durability properties of the erythrocytes of jaundiced neonates were investigated using spectral analysis and osmotic fragility. The results revealed that, there was a significant decrease in the mean cell fragility (MCF) from 0.41 for control cases to 0.298 for CNI case also the hemolytic ratio shows a sharp decay at G-6-PD conc.<4 U/gHb*. Absorption spectra of erythrocytes shows a significant decrease of splitting factor (SF) as bilirubin (Bb) conc. increases, indicating that the cells tend to convert from oxygenated to deoxygenated state with a peak at 560nm which is confirmed by SF values. It may be concluded that a severe hyperbilirubinemia may leads to irreversible damage of spheroechinocyte cells, causing cell lysis .