The literature on biologic risks, such as asphyxia, and later outcome contains many confounding issues. Earlier data may not be applicable today because of high mortality rates and significant changes in medical practice. Data from a more contemporary cohort indicate an association between arrays of biologic variables and outcome, although early developmental/behavioral measures are more predictive. Some variables had a 'sleeper effect,' which did not surface until 36 months. Suggestions for better delineation of relationships between nonoptimal risk variables and outcome are provided.