Secondary hyperparathyroidism (SHPT) is an important complication of end-stage renal disease. However, SHPT begins during earlier stages of chronic renal insufficiency (CRI), and little is known about risk factors for SHPT in this population. This study evaluated 218 patients in an ethnically diverse ambulatory nephrology practice at the University of California San Francisco during calendar years 1999 and 2000. Demographic data, comorbid diseases, medications, and laboratory parameters were collected, and independent correlates of intact parathyroid hormone (PTH) were identified by using multiple linear regression. The mean estimated GFR was 34 ml/min per 1.73 m(2) (10%-90% range, 13 to 61 ml/min per 1.73 m(2)); PTH was inversely related to GFR (P < 0.0001). The adjusted mean PTH was higher among African Americans and lower among Asian/Pacific Islanders compared with white patients (233 versus 95 versus 139 pg/ml; P < 0.0001). Moreover, among the 196 patients with GFR <60 ml/min per 1.73 m(2), the slope of GFR versus PTH was significantly steeper among African Americans than among white patients (10.6 versus 3.9 pg/ml per ml per min per 1.73 m(2); P = 0.01). After adjusting for age and diabetes, PTH was associated with a history of myocardial infarction (OR, 1.6; 95% CI, 1.1 to 2.3 per unit natural log PTH) and congestive heart failure (OR, 2.0; 95% CI, 1.3 to 2.9 per unit natural log PTH) and not associated with other co-morbid conditions. These factors should be considered when screening and managing SHPT in CRI.