The study consists of two parts. Part I is an open-label single-dose, non-fasting, multicenter study to evaluate the pharmacokinetics of paricalcitol capsules in 12 pediatric subjects ages 10 to 16 years with CKD Stages 3 and 4. Part II of this study will be conducted as a 12 week randomized double-blind, placebo-controlled study, followed by 12 weeks open-label treatment. The objective of this multicenter study is to evaluate the safety and efficacy of paricalcitol capsules in decreasing serum intact parathyroid hormone (iPTH) levels to K/DOQI target goals in 72 pediatric subjects ages 10 to 16 years with CKD Stages 3 and 4.