Abnormal mineral metabolism has the potential to significantly increase mortality in patients with chronic kidney disease, especially by the time renal replacement therapy is required. While excess phosphorus and hyperphosphatemia have long been identified as risks for increased morbidity and mortality, the roles of calcium load and serum calcium levels have been less clear. Calcium-based recommendations in the K/DOQI Clinical Practice Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease were labeled as expert opinion. The rationale behind the opinion-based recommendations is reviewed along with additional supportive information that has become available since the bone and mineral guidelines were published.