Both bone mass by densitometry and speed of sound (SOS) from quantitative ultrasound of the bone (QUS) are directly related to bone strength. However, reports of lower bone mass but higher SOS in neonates with intrauterine growth deficit lead to apparent contradictory conclusions on bone strength. Three groups of infants were studied: small for gestation (SGA) with birth weights ≤10th percentile for gestation and 2 control groups with appropriate birth weights (11th to 90th percentile) for gestation (AGA): matched to SGA group for gestation and birth weight, respectively. SOS was measured with a commercial QUS instrument (Sunlight Omnisense 7000, Sunlight Medical Ltd, Tel Aviv, Israel) and 2 manufacturer supplied ultrasound probes (CS and CR) for small bones. The SGA group had significantly (p<0.01) higher SOS compared with weight matched but gestational less matured control group by an average of 54m/s with the CS probe and 80m/s with the CR probe but not significantly different from gestation-matched AGA group. SOS values from both probes were significantly correlated (r=0.71-0.91) but were significantly different between probes. Probe failure occurred with both probes. We conclude that QUS SOS values in SGA neonates are a reflection of a continuum of intrauterine maturation of the skeleton.