THE ROLE OF SERUM APELIN IN RETINOPATHY OF PREMATURITY Objective: To evaluate the role of serum apelin as a diagnostic tool in retinopathy of prema¬turity (ROP) disease. Patients and methods: Thirty-eight preterm infants (60% male) with gestational age ranging from 30 to 36 weeks admitted to the neonatal intensive care unit, KJO Hospital, Saudi Arabia with proven diagnosis of ROP were included in the study. In addition, 27 preterm infants without ROP served as controls. All newborn infants in the study were subjected to adequate history taking, full clinical examination, and fundus examination by indirect ophthalmoscope (at 4–6 weeks) as well as determination of serum apelin at birth and at 4–6 weeks of age. Results: The study revealed that oxygen therapy longer than 7 days’ duration, cesarean section (as a mode of delivery), sepsis, mechanical ventilation, blood transfusion, premature rupture of membranes, pneumothorax, perinatal asphyxia, cardiac problems, and neonatal jaundice were considered as risk factors related to development of ROP. Serum apelin levels were significantly lower in patients than controls (P,0.001) at time of diagnosis of the disease (4–6 weeks) while no significant differences were observed in levels at birth. Conclusion: Serum apelin was found to be of significant diagnostic value in the occurrence of ROP.