> Objective: This paper describes the deliberations of an interdisciplinary group of clinical and basic scientists who met at the National Institute of Child Health and Human Development to discuss the potential role of fetal behavior in assessing fetal well being and predicting neonatal outcome. The conference focused on three aspects of fetal behavior: 1) habituation; 2) state transitions; and 3) movement. Methods: The participants consisted of 25 leaders in the fields of obstetrics, perinatal medicine, neonatology, developmental psychobiology, developmental neuroscience, developmental psychology, ethology, and mathematics. The meeting was divided into three parts. In each of these a plenary speaker (a recognized expert in his field) began the session with an overview of the scientific theme. Two respondents, with research expertise in fetal research (animal models or human fetuses) followed with remarks on the plenary talk and comments based on their own studies. At the conclusion of these comments, the participants met in small groups to discuss the plenary proceedings and their implications for assessing human fetal well being and predicting outcome. At the conclusion of the small group deliberations all of the participants reconvened in a plenary session. During this part of the meeting a rapporteur from each small group summarized their discussions. Results and Conclusions: 1) Fetal habituation: there was a general consensus that research on this aspect of fetal behavior may have a high payoff for assessing human fetal well being and predicting neonatal outcome. 2) Behavioral state transitions: participants agreed that transitions afford investigators with an indication of when (timing) and how (models) behavior changes within and between developmental periods. Knowledge of transitions during development allows for tracking of behaviors that may be necessary for the fetus to adapt to its in utero environment or prepare for its postnatal life. 3) Chaos theory and fetal movement: participants concluded that non-linear dynamics systems analysis models could be useful to analyze "noise" within a measurement system; better define time scales; and increase resolution and thereby better identify "signals."