Abstract:Objective: To determine the possible genotoxic effect of phototherapy in term infants with hyperbilirubinemia. Patients and methods: A total of 172 term infants aged 3–10 days after birth were enrolled in the study. Newborns were divided into intensive phototherapy (n = 41), conventional phototherapy (n = 46), jaundiced control (n = 43), and non-jaundiced control (n = 42) groups. DNA damage, sister chromatid exchange (SCE) frequency, plasma total antioxidant capacity (TAC) and total oxidant status (TOS) levels were measured. Results: Before phototherapy, there were no significant differences between the four groups in terms of DNA damage, SCE frequency, TAC, or TOS (p > 0.05). After phototherapy, DNA damage, SCE frequency, and TOS were significantly higher in the intensive than in the conventional group (p < 0.05). In the phototherapy-treated groups, DNA damage and SCE frequency correlated positively with TOS (p < 0.05). Conclusion: Phototherapy may induce genotoxic effect in peripheral blood lymphocytes of term infants with hyperbilirubinemia.