Aim: To determine the incidence of post-phototherapy neonatal plasma total bi lirubin (PTB) rebound. Methods: A prospective clinical survey was performed on 2 26 term and near-term neonates treated with phototherapy in the well baby nursery of the Shaare Zedek Medical Center from January 2001 to September 2002. Neona tes were tested for PTB 24 hours (between 12 and 36 hours) after discontinuation of phototherapy, with additional testing as clinically indicated. The main outc ome measure, significant bilirubin rebound, was defined as a post-phototherapy PTB ≥256 μmol/l. Phototherapy was not reinstituted in all cases of rebound, bu t rather according to clinical indications. Results: A total of 30 (13.3%) neon ates developed significant rebound (mean (SD) PTB 287 (27) μmol/l, upper range 351 μmol/l). Twenty two of these (73%) were retreated with phototherapy at mea n PTB 296 (29) μmol/l. Multiple logistic regression analysis showed significant risk for aetiological risk factors including positive direct Coombs test (odds ratio 2.44, 95%CI 1.25 to 4.74) and gestational age < 37 weeks (odds ratio 3.21 , 95%CI 1.29 to 7.96). A greater number of neonates rebounded among those in wh om phototherapy was commenced ≤72 hours (26/152, 17%) compared with > 72 hours (4/74, 5.4%) (odds ratio 3.61, 95%CI 1.21 to 10.77). Conclusion: Post-photot herapy neonatal bilirubin rebound to clinically significant levels may occur, es pecially in cases of prematurity, direct Coombs test positivity, and those treat ed ≤72 hours. These risk factors should be taken into account when planning pos t-phototherapy follow up. Aim: To determine the incidence of post-phototherapy neonatal plasma total bi lirubin (PTB) rebound. Methods: A prospective clinical survey was performed on 2 26 term and near-term neonates treated with phototherapy in the well baby nursery of the Shaare Zedek Medical Center from January 2001 to September 2002. Neona tes was tested for PTB 24 hours (between 12 and 36 hours) after discontinuation of phototherapy, with additional testing as clinically indicated. The main outc ome measure, significant bilirubin rebound, was defined as a post Phototherapy was not reinstituted in all cases of rebound, bu t rather according to clinical indications. Results: A total of 30 (13.3%) neon ates developed significant rebound (mean (SD) PTB 287 ( Twenty two of these (73%) were retreated with phototherapy at mea n PTB 296 (29) μmol / l. Multiple logistic regression analysis showed significant risk for aetiological risk factors inc luding positive direct Coombs test (odds ratio 2.44, 95% CI 1.25 to 4.74) and gestational age <37 weeks (odds ratio 3.21, 95% CI 1.29 to 7.96). A greater number of neonates rebounded among those in wh om phototherapy was commenced Conclusion: Post-photot herapy neonatal bilirubin rebound to clinically significant levels (% may occur, es pecially in cases of prematurity, direct coombs test positivity, and those treat ed ≤72 hours. These risk factors should be taken into account when planning pos t-phototherapy follow up.