This report describes the experimental design, methods, and baseline characteristics of patients enrolled in a Veterans Administration Cooperative Study on the effect of aspirin (325 mg t.i.d.) and dipyridamole (75 mg t.i.d.) (110 patients), or placebo (121 patients) on major vascular outcome variables in noninsulin-dependent diabetic patients with either a recent amputation for gangrene (n = 207) or active gangrene (n = 24). It also describes the baseline characteristics of the patients. A total of 231 patients of 563 screened (41%) were enrolled at 11 participating V.A. Medical Centers during a 39 month period. The median age at entry was 60 years, the median duration of diabetes was 10 years, and weight was 110% of desirable. All patients were men. Sixty-eight percent were treated with insulin and 32% with diet alone. Only 42% were smokers at entry, 40% had retinopathy, 61% sensory neuropathy, 42% hypertension, and 29% had a history of myocardial infarction, angina, and/or congestive heart failure. Thirteen percent had a history of cerebrovascular disease. Despite randomization, the treatment group had an increased frequency of a history of cerebrovascular disease (p = 0.01), diagnosed as stroke (p = 0.03), a finding suggesting that the treatment group was at a slightly increased risk for vascular disease upon enrollment in the study. Other baseline variables did not differ significantly between the two groups. This study should provide definitive data on the efficacy of these doses of antiplatelet agents in preventing further vascular disease in diabetic men with gangrene or recent amputation for gangrene, using death due to vascular disease and subsequent amputation of the opposite extremity for gangrene as major outcome variables. It should also give useful information on the effect of antiplatelet therapy on vascular outcome variables such as same side amputations, myocardial infarction, stroke, transient ischemic attack, retinopathy, and renal failure. Finally, the study should provide useful data on the natural history and significance of risk factors in this patient population.