This study evaluates the effects of neonatal behavioral assessments and heelsticks on transcutaneous oxygen tension (TcPO2) in 37 preterm neonates from a neonatal intensive care unit. Two behavioral assessments were evaluated, the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) and the Neurobehavioral Assessment for Preterm Infants (NAPI). TcPO2 during heelsticks was used as a comparison because reliable decreases have typically been noted during heelsticks. Although the heelsticks resulted in significant declines in TcPO2, the behavioral assessments led to only negligible changes in TcPO2. Observed changes during the behavioral assessments occurred in a small number of infants, primarily during the few test procedures administered to the infants outside of their isolettes. Accordingly, it is suggested that time outside the isolette and associated temperature changes may be more critical variables than the assessments per se.