Neonatal jaundice in most cases is a benign condition in the newborn that does not require additional interventions other than observation. However, the manifestations of hyperbilirubinemia under certain conditions may be one of the first clinical signs of disorders of the functional state of the hepatobiliary system (HBS), in which case this process is not considered physiological and requires appropriate clinical observation and additional examination. Contributing factors to the development of HBS dysfunction in newborns may be: concomitant perinatal pathology, isoimmunization, congenital defects in the metabolism of enzymes involved in the transformation and excretion of bilirubin, and so on. Purpose — based on a comprehensive analysis of specific clinical and laboratory indicators to determine the most characteristic pathogenetic syndromes, which are the basis for the formation of disorders of the functional state of the hepatobiliary system in the presence of clinical manifestations of jaundice in newborns. Materials and methods. 164 full-term infants were included in the study. The main study group І (92 children with clinical manifestations of jaundice on the background of perinatal pathology) was divided into 2 subgroups depending on the severity of the newborn in the early neonatal period: IA subgroup (46 pers.) — children with moderate severity and IB subgroup (46 people) — children whose condition was assessed as severe. Group II (comparison group) consisted of 72 healthy full-term newborns. Biochemical studies of serum in newborns were performed using an analyzer «ULTRA» company «Kone» (Finland, reagents of the company) and an apparatus for electrophoresis «PARAGON» company «Bekman» (Austria, reagents of the company) in the biochemical laboratory of the maternity hospital. For reliable analysis of statistical data, the assessment was performed using the software SpssStatistica, 2010; Excel, 2016. Procedures, logic and interpretation of the obtained analysis results were based on the main provisions of medical and biological statistics. The comparison of quantitative indicators with the normal distribution was performed using Student's t-test. Results. Analysis of the functional status of HBS in newborns with hyperbilirubinemia with perinatal pathology showed the following clinical signs of dysfunction: jaundice, hepatosplenomegaly, intestinal dysfunction, manifestations of hypoglycemia, anemic and hemorrhagic syndrome. Disorders of bilirubin metabolism were confirmed by an increase in the blood serum level of bilirubin due to the indirect fraction. Indicators of ALT and AST activity tended to increase considering the severity of perinatal pathology. The value of LDH also correlated with the severity of the condition and was highest in children of the IB subgroup. The activity of ALP tended to increase in children of the IA subgroup, while children of the IB subgroup showed lower activity compared to control. GGT activity in neonates of the observation subgroups showed a tendency to decrease compared with the control. Analysis of the white blood spectrum revealed a decrease in the level of both total protein and albumin levels in children of IA and IB subgroups compared with the control, with more expressed changes observed in newborns with severe perinatal pathology. It was found that the main pathogenetic syndromes and formation of dysfunction of the hepatobiliary system in the presence of clinical signs of hyperbilirubinemia in perinatal pathology are: cytolysis syndrome, cholestasis and protein-synthetic insufficiency, the severity and prevalence of which corresponds to the clinical symptoms and severity of the disease. Conclusions. The main clinical manifestations of disorders of the functional state of the hepatobiliary system in hyperbilirubinemia in perinatal pathology in newborns are: jaundice, hepatosplenomegaly, intestinal dysfunction, in more severe cases — hypoglycemia, anemia and hemorrhagic disorders. In-depth analysis of biochemical parameters of blood in newborns showed that the main syndromes of the pathogenesis of HBS dysfunction are: cytolysis syndrome, which is characterized by increased activity of AST, ALT and LDH; cholestasis syndrome, which is manifested by an increase in blood levels of total bilirubin, cholesterol, increased activity of ALP enzymes, GGT and protein — synthetic deficiency syndrome, which is confirmed by a decrease in total protein, albumin, cholinesterase, urea and glucose. Significant violations of the functional state of the hepatobiliary system in the presence of jaundice in severe perinatal pathology in newborns that were discovered indicate the need for timely diagnosis for appropriate therapeutic correction. The research was carried out according to the principles of the Declaration of Helsinki. The study protocol was approved by the BSMU LEK for all the participants. Examination of children was conducted with the consent of parents after a preliminary explanation of the purpose, methods and scope of laboratory research methods. No conflict of interest was declared by the authors. Key words: newborn, jaundice, hepatobiliary system.