The goal of the study was to assess how accurately patient volume predicts quality of care for VLBW infants and to compare volume with direct indicators, such as patient mortality. Data came from 332 NICUs in the Vermont Oxford Network of providers from across the United States. This network includes 40 percent of the NICUs in the United States and accounts for 50 percent of annual VLBW infant admissions. The study population included all 94,110 infants between 501 and 1,500 grams born in network hospitals between 1995 and 2000. The study found that referrals for VLBW infants that rely on indirect measures such as volume are at best minimally effective for predicting outcomes and may unfairly penalize high-quality providers that have lower volumes. By contrast, direct measures such as infant deaths are more useful quality indicators for the purposes of selective referral: They predict future mortality rates more accurately and could therefore save infant lives.