This open label 4 month study will evaluate efficacy (blood pressure lowering effects) and safety of lisinopril in children 1-18y whose parents grant permission to participate. This dose titration study is being conducted to support the statement that personalized titration of lisinopril (based on blood pressure and renin-aldosterone ratio) can increase patient response.

Inclusion Criteria:

• Parental consent must be granted
• Patient age: 1y - 18 y
• Documented diagnosis of hypertension as defined in the National Heart, Lung and Blood Institute (NHBLI) 4th report, 2004
• No reversible cause found on diagnostic work-up for hypertension
• Children older than 6y: 24h blood pressure monitoring confirms the diagnosis of hypertension

Exclusion Criteria:

• Pregnancy
• Sexually active girls can only be included in the trial if they use an adequate form of birth control; during and until 30 days after ending the trial
• Following abnormal laboratory values: Hyperkaliemia (serum potassium > 5.3mmol/L); Anemia (hemoglobin < 8g/dL); AST or ALT > 3 times the upper limit of reference range; Total bilirubin > 3 times the upper limit of reference range
• Abnormalities of the oral cavity that can influence intake of medication
• Known sensitivity to ACE-inhibitors
• Known lactose intolerance
• History of angioedema
• Unilateral or bilateral stenosis of the renal artery
• Diagnosis of heart failure (NYHA Class II-IV)
• History of coarctation of the aorta
• Current treatment with: other drugs influencing the renin-angiotensin-aldosterone system; lithium; potassium sparing diuretics; non-steroidal anti-inflammatory drugs; aspirin; oral antidiabetic medication