Two groups of neonates, 30 cases with hyperbilirubinemia (307.8 +/- 99.86 
mumol/L) and 30 normal newborns (control group with bilirubin 80.37 +/- 35.74 
mumol/L), were evaluated with Neonatal Behavioral Assessment Scale (NBAS) and 
followed up at the age of 2 months and 5 months. All cases in the two groups 
were evaluated with NBAS at ages of 2-3 days, 12-14 days and 26-28 days. The 
results showed that there were statistically significant differences between the 
two groups in the aspects of attention and social responsiveness, the ability to 
modulate state of consciousness, the motor integrity and the reflexes. We also 
found that while the level of bilirubin was below 205.2 mumol/L, there was no 
correlation between the level of bilirubin and NBAS (r = -0.095, P > 0.02), but 
when bilirubin was at or above the level of 205.2 mumol/L, there was significant 
negative correlation (r = -0.53, P < 0.001) between the two. The follow-up 
revealed that 9 of 23 jaundiced infants had abnormal auditory reactions or 
abnormal muscle tonus at the age of 2 months; 8 of the 9 infants recovered, but 
1 still had abnormal muscle tonus by the age of 5 months. The study suggests 
that hyperbilirubinemia above the level of 205.2 mumol/L would affect neonatal 
behavior and the greater the severity of jaundice, the more significant the 
influence on neonatal behavior. The effects on some jaundiced infants may last 5 
months or more. NBAS is a valuable scale for early detection of mild brain 
dysfunctions which are less obvious on clinical examination.