This study was conducted to determine the incidence and magnitude of post-phototherapy bilirubin rebound in neonates. Subjects included inborn neonates needing phototherapy for hyperbilirubinemia. Standard guidelines were used to start and stop phototherapy. Rebound bilirubin was measured 24+/-6 h after stopping phototherapy. Significant bilirubin rebound (SBR) was defined as post-phototherapy bilirubin level needing reinstitution of phototherapy. Among 245 neonates with hyperbilirubinemia, post-phototherapy bilirubin estimation was done in 232 neonates. A total of 17 (7.3%) neonates developed SBR. In neonates with SBR, bilirubin increased by 2.3 mg/dL (95% CI 1.6-3.0) after stopping phototherapy. Risk factors for SBR included birth at >35 weeks of gestation (RR 4.3, 95% CI 1.5-12.0), birthweight <2000 g (RR 3.2, 95% CI 1.0-10.3) and onset of jaundice at >60 h of age (RR 3.3, 95% CI 1.2-9.0). Post-phototherapy discharge and follow-up planning should take into account these risk factors.