• Early weight-change patterns were studied in 101 passively addicted neonates. Newborns showing mild abstinence and not requiring pharmacologic treatment lost an average of 4.0% of birth weight, reached a weight nadir on day 3, and regained birth weight by days 7 to 8. Newborns treated with either paregoric or phenobarbital for more severe signs of abstinence lost an average of 6.3% of birth weight, reached a nadir on days 6 to 7, and regained birth weight only by days 13 to 14. Despite comparable birth weights and energy intakes, treated newborns weighed 95 g less than untreated neonates on day 10 when the untreated neonates were discharged. In light of abnormal early weight-change patterns seen with more severe abstinence, both strict control of abstinence and provision of additional individualized nutritional support seem warranted.