Large observational studies examining the association between anemia and "hard" clinical outcomes are rare in patients with chronic kidney disease (CKD). We used the General Medicare 5% Denominator Files to identify patients aged 67 years or more with CKD on December 31, 1999. Outcomes in the ensuing 2 years were compared in patients with and those without anemia (entry period, 1998-1999; follow-up period, 2000-2001). Of 41,522 CKD patients identified, 49.0% had claims of anemia diagnosis. The factors associated (p< 0.0001) with anemia included older age, female gender, black race, and all 10 comorbid conditions studied; adjusted odds ratios (ORs) exceeded 1.5 for age 80 years old or older (OR, 1.54 compared to <70 years), for black race (OR, 1.52), and for co-existing diagnoses of congestive heart failure (OR, 1.64), gastrointestinal bleeding (OR, 3.65), and liver disease (OR, 2.16). During the follow-up period, outcome event rates (expressed per 1000 patient-years) were as follows: renal replacement therapy, 23.5; death, 186.4; congestive heart failure, 390.0; atherosclerotic vascular disease, 410.5; and first hospitalization, 552.6. Using proportional hazards modeling, the presence of anemia was associated (p < 0.0001) with the following adjusted hazards ratios: atherosclerotic vascular disease, 1.09; congestive heart failure, 1.14; renal replacement therapy, 2.61 and death, 1.40. A diagnosis of anemia is present in nearly half of all patients with CKD, aged 67 years or more, a group at very high risk of cardiovascular disease, hospitalization, end-stage renal disease, and death. Anemia is associated with each of these events.