Preterm infants weighing less than 1500 g routinely undergo a series of eye examinations to screen for retinopathy of prematurity (ROP). Mydriatic eye drops used for pupil dilatation while these examinations may be absorbed by nasopharyngeal mucosa and gastrointestinal system that may cause neurological and gastrointestinal side effects rarely. We aimed to evaluate the effect of mydriatic eye drops on cerebral and mesenteric tissue oxygenation by near infrared spectroscopy (NIRS), in very low birth weight (VLBW) infants. Eleven preterm infants with a gestational age of < 32 weeks and/or birth weight < 1500gr were included the study. Infants with intracranial hemorrhage (>grade II), PDA, major congenital anomalies, major heart disease, infection, anemia, thyroid disease, acidosis, history of perinatal asphyxia and surgery, not feeding orally, were excluded the study. Cerebral and mesenteric tissue oxygenation were measured by NIRS probes that located forehead and umbilical region before and after the mydriatic eye drops. Eleven (6 female, 5 male) infants were included the study. The median gestational age, birth weight, postnatal age and body weight during examination were 29 weeks, 1190g, 39 days and 1700g, respectively. Before the mydriatic eye drops mean cerebral and mesenteric rSO2 were 63.0±7.6 and 54.9±10.1, respectively. After the eye drops mean cerebral and mesenteric SO2 were 60.0±10 and 51.7±9.9, respectively. Although the slightly decrease in oxygenation after mydriatic eye drops there were no statistically significant differences (p=0.6 and p=0.1). We believe that this difference may reach statistically significant levels in large study population.