Calcium (Ca) supplementation is used frequently in neonates in the early postnatal days or following asphyxia and resuscitation. The rationale for this supplementation has been based on the laboratory finding of low serum total Ca concentrations. Recent studies have shown that total Ca is poorly correlated to ionized Ca++ in the serum. Serum total and ionized Ca++ with concurrent blood pH were measured sequentially, with an ICA 1 ionized Ca++ Analyzer (Radiometer), in 10 term infants (BW=3381±772g, GA=40±1.5 wks) at 0, 4, 24 and 48 hours postnatally. All infants had fetal distress with moderate to severe variable or late decelerations in their fetal heart rate tracings. Eight infants required emergency Caesarian Section, and 2 were forceps assisted vaginal deliveries. Apgar scores were 1.7±0.9 and 7.2±1.5 at 1 and 5 minutes respectively. Serum total creatine phosphokinase (CPK) was elevated at 24 and 48 hours and the MB fraction of the CPK isoenzymes was the fraction most elevated. Serum total Ca was 11±1.1 at birth and fell to 8.7±0.8 and 9.3±1.8 mg/dl at 24 and 48 hours respectively. In contrast, the actual ionized Ca++ remained unchanged, being 1.2±0.4, 1.2±0.05, 1.2±0.08 and 1.2±0.05 mM/dl at 1, 4, 24 and 48 hours respectively. In view of the reported complications of excess ionized Ca++ producing vasospasm, ischemia, angina, cardiac infarction in adults, and the hazards of intravenous Ca administration in neonates, Ca supplementation should be used with caution. Data from this study suggest that asphyxiated neonates do not require routine Ca supplementation.