The efficacy and wavelengths of fiberoptic phototherapy and conventional daylight phototherapy were compared in a relatively larger series of term newborns with nonhemolytic and significant hyperbilirubinemia than reported in previous studies. One hundred and nine term newborns were randomly assigned to receive either fiberoptic phototherapy on a fiberoptic phototherapy pad or overhead conventional phototherapy consisting of five daylight fluorescent lamps. Although the average spectral irradiance measured during the study period was significantly greater in the fiberoptic phototherapy group (9.2+/-1.2 microW/cm2/nm vs 7.1+/-1.1 microW/cm2/mm, p < 0.05), conventional phototherapy was significantly more effective in decreasing bilirubin levels: the duration of exposure to phototherapy was significantly shorter (49.4+/-14.4 hours vs 61+/-13.1 hours, p < 0.05), and overall bilirubin decline rate as mg/dl/h and percent/h was significantly greater in the conventional phototherapy group (0.15+/-0.06 mg/dl/h vs 0.11+/-0.05 mg/dl/h, and 0.81+/-0.34 percent/h vs 0.60+/-0.28 percent/h, p < 0.05). There were four failures of phototherapy in the fiberoptic phototherapy group whereas no phototherapy failure was observed in the conventional phototherapy group (p < 0.05). The emission spectrum of the daylight fluorescent lamp revealed a broad emission between the violet and red spectra with tiny narrow peak emission bands in 405 nm, 436 nm, 546 nm and 577 nm, while a broad emission through the blue and green wavelengths (mainly in the green spectrum) without any peak emissions was detected in the tungsten-halogen lamp of the fiberoptic phototherapy system. Conventional phototherapy with daylight fluorescent lamps should be preferred to fiberoptic phototherapy administered with fiberoptic phototherapy and in the treatment of term newborns with nonhemolytic hyperbilirubinemia.