Changes in calorie intake and weight gain were evaluated in five children with cystic fibrosis (CF) who received behavioral intervention and four children with CF who served as wait list controls. The behavioral intervention was a 6-week group treatment that provided nutritional education plus management strategies aimed at mealtime behaviors that parents find most problematic. The control group was identified prospectively and was evaluated on all dependent measures at the same points in time pre- and posttreatment as the intervention group. Difference scores on calorie intake and weight gain from pre- to posttreatment were compared between groups using t tests for independent samples. The behavioral intervention group increased their calorie intake by 1,032 calories per day, while the control group's intake increased only 244 calories per day from pre- to posttreatment [t(6) = 2.826, p = 0.03]. The intervention group also gained significantly more weight (1.7 kg) than the control group (0 kg) over the 6 weeks of treatment [t(7) = 2.588, p = 0.03] and demonstrated catchup growth for weight, as indicated by improved weight Z scores (-1.18 to -0.738). The control group showed a decline in weight Z scores over this same time period (-1.715 to -1.76). One month posttreatment, the intervention was replicated with two of the four children from the control group. Improved calorie intake and weight gain pre- to posttreatment were again found in these children. At 3- and 6-month follow-up study of children receiving intervention, maintenance of calorie intake and weight gain was confirmed. No changes were found on pulmonary functioning, resting energy expenditure, or activity level pre- to posttreatment. This form of early intervention appears to be promising in improving nutritional status and needs to be investigated over a longer period of time to evaluate the effects of treatment gains on the disease process.