1. In thirteen consecutive instances, individuals with acute thrombophlebitis were given ultraviolet blood irradiation .

2. In all thirteen, a rapid disappearance of pain and tenderness was observed, usually within twenty-four to forty-eight hours following a single blood irradiation.

3. A drop to normal of abnormally high temperatures, when present, was found to occur within forty-eight to seventy-two hours.

4. Edema subsided completely in twelve of the thirteen cases, the disappearance time varying from thirteen to fifteen days. In the thirteenth case, a marked induration was associated with edema and neither had disappeared when the patient left the hospital on the eighth postirradiation day.

5. A complete absence of untoward effects in all patients treated was evident.

6. Of the thirteen cases, five were good examples of the failure of sulfa drugs plus local heat, bedrest, and elevation of the affected extremity to control thrombophlebitis; four received only ultraviolet blood irradiation and bedrest; three had failed to respond to local heat, bedrest, and elevation of the affected extremity; and one represented the absence of any effect, in fifty days, of four therapeutic nerve blocks to influence the disease process; an apparent permanent indurative damage had occurred.