Diabetes mellitus is a risk factor for target-organ damage/clinical cardiovascular disease in older persons. A retrospective analysis was performed of charts from all older persons (506 men and 1497 women, mean age 80 +/- 8 years) seen during the period from 1 January 1998 to October 1998 at an academic hospital-based geriatrics practice, to investigate the prevalence of diabetes mellitus, and the prevalence, in patients with diabetes, of target-organ damage/clinical cardiovascular disease, hypertension, hypertension or dyslipidaemia, obesity, the drugs used to treat diabetes, and poor glycaemic control. Diabetes mellitus occurred in 127 of 1150 whites (11%), in 93 of 444 African-Americans (21%), in 111 of 381 Hispanics (29%), and in four of 28 Asians (14%) (P < 0.001 comparing Hispanics with whites and comparing African-Americans with whites; P < 0.01 comparing Hispanics with African-Americans). Of 335 patients with diabetes, 146 (44%) had coronary disease, 94 (28%) had stroke or transient cerebral ischaemic attack, 86 (26%) had peripheral arterial disease, 65 (19%) had heart failure, 107 (32%) had nephropathy, 71 (21%) had retinopathy, 47 (14%) had neuropathy, 284 (85%) had target-organ damage/clinical cardiovascular disease, 252 (75%) had hypertension, 300 (90%) had hypertension or dyslipidaemia, and 152 (45%) had obesity. The prevalence of stroke or transient cerebral ischaemic attack was greater in older African-Americans with diabetes mellitus than in older whites with diabetes mellitus (P < 0.02). The prevalence of diabetic nephropathy and of target-organ damage/clinical cardiovascular disease was greater in older African-Americans with diabetes mellitus than in older whites (P < 0.02) and Hispanics (P < 0.05) with diabetes mellitus. Increased concentrations of glycosylated haemoglobin (> 7%) occurred in 28 of 86 African-Americans (33%), in 69 of 104 Hispanics (66%), and in 23 of 118 whites (19%) (P < 0.001 comparing Hispanics with whites and comparing Hispanics with African-Americans; P < 0.05 comparing African-Americans with whites). The prevalence of diabetes mellitus in 2003 older persons seen in an academic hospital-based geriatrics practice was 17% and was greater in Hispanics than in whites or African-Americans, and greater in African-Americans than in whites. The prevalence of target-organ damage/clinical cardiovascular disease was 85% in 335 older patients with diabetes. The prevalence of stroke or transient cerebral ischaemic attack was greater in older African-Americans with diabetes mellitus than in older whites with the disorder. The prevalence of diabetic nephropathy and of target-organ damage/clinical cardiovascular disease was greater in older African-Americans with diabetes mellitus than in older whites and Hispanics with diabetes mellitus. The prevalence of poor glycaemic control was greater in Hispanics than in whites or African-Americans and greater in African-Americans than in whites.