Chronic kidney disease (CKD) can result in a loss of ability to filter and excrete phosphate. The body's attempt to adjust to an increased level of phosphate in the blood can result in elevated levels of hormones and minerals resulting in serious clinical consequences. This study is being conducted to evaluate the safety and efficacy of lanthanum carbonate in lowering high levels of phosphorus in the blood in subjects with CKD Stages 3 and 4 compared to placebo.

Inclusion Criteria:

• Under a physician's care for CKD for > 2 months and are not expected to begin dialysis for 4 months
• Screening estimated GFR of 15-59 mL/1.73 m2
• Serum phosphorus >= 4.7 mg/d following washout

Exclusion Criteria:

• Requiring treatment with cinacalcet HCI or compounds containing phosphate, aluminum, calcium or magnesium
• Rapidly progressing glomerulonephritis
• Cirrhosis or other clinically significant liver diseases
• Past or present uncontrolled peptic ulcer, Crohn's disease, malignancy or recent GI bleed