The drug use in 228 persons with diabetes was studied and compared with that of sex- and age-matched non-diabetic controls--all of whom were found by the screening of a well-defined Danish population aged 60-74 years. Ninety per cent of the diabetics had non-insulin-dependent diabetes mellitus (NIDDM), as evaluated by a glucagon-C-peptide test. Information on daily use of prescribed and non-prescribed drugs was obtained by questionnaires and interviews. More than 80% of the diabetics used drugs daily, compared to 55% of control subjects (P less than 0.00001). Among subjects using drugs diabetics, on average, used 70% more defined daily doses (DDD) than controls, even when antidiabetics were excluded. There was no difference in the number of drug users among subgroups of diabetics when divided according to antidiabetic treatment but tablet-treated diabetics, on average, used 20% fewer DDD than other diabetics. Cardiovascular drugs were the most commonly used drugs. Diabetics in all antidiabetic treatment groups used significantly more cardiovascular drugs than non-diabetics. Diabetics treated with oral antidiabetics used fewer cardiovascular drugs than insulin- and diet-treated diabetics. The estimated cost of drug therapy was more than 2.5 times higher for diabetics than for the control group. Our results reflect the increased morbidity among elderly diabetics and emphasise, together with other aspects of costs of diabetes in the elderly, the need for allocating resources for the prevention of NIDDM instead of the treatment of its complications.