Efficacy in pediatrics can be extrapolated from adequate and well controlled adult trials if it is reasonable to assume that disease progression and response to intervention in pediatrics is similar to adults. The knowledge of pharmacokinetics (PK) and exposure-response (ER) plays an important role in dose selection. If it is reasonable to assume similar ER relationships between pediatrics and adults, then a pediatric dose is selected to achieve exposures similar to adult therapeutic dose. However, if this assumption cannot be made, then ER relationship can be used to select doses in children. The purpose of this communication is to highlight how PK, ER and clinical data are used to select doses in children using the example of infliximab treatment of ulcerative colitis (UC). This topic was discussed at the FDA Gastrointestinal Drugs Advisory Committee meeting on July 21, 2011. An open-label, randomized, parallel-group study was conducted to assess safety and efficacy of infliximab induction and maintenance treatment in 60 patients aged 6 through 17 years with moderately to severely active UC despite adequate conventional therapy. The induction regimen was 5 mg/kg i.v. administered at weeks 0, 2, and 6. Responders at week 8 were randomized to 5 mg/kg q8 or q12 week dosing regimen (maintenance treatment) with an option to increase the dose or dosing frequency in case of loss of response. FDA conducted post-hoc ER analyses to examine whether the dosing regimen is appropriate. Logistic regression analyses of infliximab serum concentration and clinical response (week 8) or remission (week 54) were conducted. A similar analysis was also performed using data from adult UC clinical trials. During the induction phase, ER was similar in pediatrics and adults. Approximately 70% of children and adults had clinical response at week 8 with concentration >20 μg/mL. Because ER was similar, the pediatric dose is based on obtaining similar infliximab exposures. Following 5 mg/kg induction dose, median serum concentrations in pediatrics (29 μg/mL) were similar to adults (33 μg/mL). Limited data in the maintenance phase precluded the evaluation of ER; therefore, pediatric dose selection depended on PK and clinical data. Steady-state trough levels in pediatrics (1.9 μg/mL) were slightly lower than adults (2.5 μg/mL). However, based on adult ER relationship, slightly lower exposures do not appear to result in lower response in pediatrics. Furthermore, the remission rate at week 54 in adults (35%) and pediatrics (38%) after 5 mg/kg q8 dose was also similar. In summary, similar PK and ER in pediatrics and adults supported the 5 mg/kg induction dose. Although, ER was not demonstrated in pediatrics in the maintenance phase, PK and clinical observations supported the maintenance dose. Extrapolation of efficacy in pediatrics from adults increases efficiency of pediatric drug development by maximizing use of adult data and avoids unnecessary pediatric trials. PK and ER analysis have a critical role in dose selection. The knowledge gained about PK and drug effects in adults should be leveraged to guide pediatric drug development to expedite access to safe and effective medicines for pediatrics.