We treated 14 patients suffering from critical limb ischemia (CLI) as defined by the Consensus Document, and in whom possibilities of surgical or percutaneous arterial reconstruction were excluded, by PGE1 60 µg i.v. daily during 3 weeks. Effects were evaluated by clinical, macrocirculatory and microcirculatory parameters during a follow-up of 1 year. After treatment with PGE1·, we noted a significant reduction in analgesic use and in pain score. The average tcpO2 values on the forefoot in the supine and sitting positions, with or without inhalation of O2 through a face mask, showed a significant improvement after 3 weeks, as well as capillary stage. Laser Doppler flux did not change, but was significantly higher in diabetic patients than in nondiabetics with CLI. In 4 patients (28%) no improvement could be found after 3 weeks’ treatment. Although in 6 patients the improvement lasted for up to 4 months, the legs eventually deteriorated. In 4 patients (28%) the legs were preserved after 1 year without further active therapy. No patient with initial tcpO2 values above 40 mm Hg in the supine and 100 mm Hg in the sitting positions during O2 inhalation lost a leg. Although other effects like local care could have influenced the outcome favorably, we noticed a beneficial albeit transient effect of PGE1 for the majority of our patients with CLI. TcpO2 measurements with O2 inhalation might be a valuable predictor of a positive long-term res