This was a 52-week, multicenter, open-label study to determine the safety, tolerability and pharmacokinetics of TOPROL-XL (metoprolol succinate) extended-release tablets (metoprolol CR/XL) in hypertensive pediatric subjects. The study population included school age children (age 6 to 12 years < Tanner Stage 3) and adolescents (> 12 years old or > Tanner Stage 3 to 16 years old) of both genders. Because response to some therapies in adult hypertension appears to be different in black and non-black populations, the recruitment will have a mixture of black and non-black subjects. Pharmacokinetic measurements were performed on a subset of patients. Thirty subjects (15 subjects each in the 6 to 12 year age group and the 13 to 16 year age group) had a series of blood samples drawn. All subjects had a trough plasma level taken 24 hours after the last dose of open-label metoprolol CR/XL (Visit 18) with the exception of those subjects who completed Protocol 307B (16 week open-label treatment).