Failure-to-thrive (FTT) is categorized as organic (OFTT) or nonorganic (NFTT). Traditionally, it has been taught that children with OFTT are unable to grow well in spite of adequate care (calories, nurturance, medical supervision), whereas NFTT children will grow well when given adequate care. We undertook this study to determine whether NFTT and OFTT children could grow at similar rates when treated by a specialized multidisciplinary team that provided concrete, individualized therapies including psychosocial support, medical care, and hypercaloric diets. Eighty-six children were enrolled on referral to our outpatient FTT consultative clinic; 64 had NFTT and 22 had OFTT. Growth quotient analysis was used to determine growth outcomes over a 6-month follow-up period. Growth at a rate paralleling the growth curve produces a GQ equal to 1. Growth 2 times as rapid as expected gives a GQ = 2. Children in both groups grew extremely well. For NFTT, GQ = 1.67 +/- 0.56 (SD); for OFTT, GQ = 1.81 +/- 0.37 (SD), p = NS. OFTT children grew just as well as NFTT children when given adequate calories for catch-up growth. Our data indicate that weight gain alone cannot reliably differentiate OFTT from NFTT, as has been traditionally taught. They suggest that we make every attempt to maximize caloric intake in FTT children. They also suggest that a multidisciplinary team consisting of a pediatrician, child psychiatrist, nutritionist, nurse clinician, and social worker may be successful in managing FTT children.