This study was a multi-center, open-label, single-sequence, crossover study to evaluate the pharmacokinetics (PK), safety and tolerability of SC-administered GAMUNEX-C in pediatric PI subjects (ages 2-16). The study consisted of a Screening Phase, Run-in Phase, two treatment phases (an IV Phase and a SC Phase), and an End of Study/Early Termination (EOS/ET) visit. Run-in phase: 3 - 4 months, IV Phase: ~ 4 - 5 weeks, SC Phase: 12 weeks, and End of Study/Early Termination (EOS/ET) visit: one week after SC Week #12.