The objective of this study was to determine the prevalence and odds of major depression and the incremental effect of major depression on utilization, lost productivity and functional disability in individuals with common chronic medical disorders. Data on 30,801 adults from the 1999 National Health Interview Survey were analyzed. The 12-month prevalence and age/sex-adjusted odds of major depression were calculated for adults with hypertension (HTN), diabetes mellitus (DM), coronary artery disease (CAD), congestive heart failure (CHF), stroke or cerebrovascular accident (CVA), chronic obstructive pulmonary disease (COPD) and end-stage renal disease (ESRD). The association between chronic condition status (with and without major depression) and utilization, lost productivity and functional disability was determined by controlling for covariates. The 12-month prevalence and age/sex-adjusted odds of major depression by chronic conditions were as follows: CHF, 7.9% [odds ratio (OR)=1.96]; HTN, 8.0% (OR=2.00); DM, 9.3% (OR=1.96); CAD, 9.3% (OR=2.30); CVA, 11.4% (OR=3.15); COPD, 15.4% (OR=3.21); ESRD, 17.0% (OR=3.56); any chronic condition, 8.8% (OR=2.61). Compared to adults without chronic conditions, those with chronic conditions plus major depression had greater odds of > or = 1 ambulatory visit [OR=1.50; 95% confidence interval (95% CI)=1.28, 1.77]; > or = 1 emergency room visit (OR=1.94; 95% CI=1.55, 2.45); and > or = 1 day in bed due to illness (OR=1.60; 95% CI=1.28, 2.00); and functional disability (OR=2.48; 95% CI=1.96, 3.15). The 12-month prevalence and odds of major depression are high in individuals with chronic medical conditions, and major depression is associated with significant increases in utilization, lost productivity and functional disability.