Six diabetic patients with infected foot lesions (mean age 64 years) and six male patients (mean age 71 years) with ischemic acral ulceration due to advanced peripheral arterial occlusive disease were treated with 200 mg ofloxacin b.i.d. The necrotic margin tissue concentrations of ofloxacin determined by HPLC and confirmed by microbiological assay were in the same range (1.6 to 6.4 mg/kg) as plasma levels (1.6 to 5.9 mg/l). No difference of plasma and tissue concentrations was found between patients with peripheral vascular disease and diabetics, respectively. After three weeks treatment bacterial wound pathogens disappeared in 7 subjects, changed in 4 patients and were resistant in one patient. Clinical improvement appeared in 9 of 12 patients after three weeks of therapy. Satisfactory tissue levels of orally administered ofloxacin were achieved in the infected necrotic tissue area of diabetic and non-diabetic patients with impaired peripheral arterial circulation.