Improvement of the desiccation of the ocular surface as well as the preservation of tear components is important in the treatment of dry eye. As it has been reported that preserved serum and tear have similar components such as EGF, vitamin A, and TGF-beta, serum application is often an effective method of treating dry eye symptoms. In this study, we evaluated the efficacy of autologous serum application for the treatment of severe dry eye. Twenty-six patients with severe dry eye; 21 with Sjogren's syndrome (SS), 5 with non-SS dry eye, were recruited. All the patients were female. The mean age was 57.2 years (range 29-78). The subjects had moderate to severe symptoms that did not respond to conventional treatment. Schirmer values were less than 10 mm with nasal stimulation in all patients. Autologous serum was prepared from the patients' blood and diluted to 20% by saline. The patients were instructed to use the autologous serum application four or eight times a day. The efficacy measures were symptoms of ocular discomfort (stable, improved, remarkably improved); rose bengal staining (graded on a scale from 0 to 9); fluorescein staining (graded on a scale from 0 to 3); and Schirmer test, before and two months after treatment. The percentages of patients whose symptoms of ocular discomfort were evaluated to have improved with 4 times instillation and 8 times instillation were 57.5% and 94.1%, respectively. Rose bengal staining and fluorescein staining were significantly decreased in the 8 times instillation group, from 7.0 to 4.7 and from 2.3 to 1.4, respectively. There were no adverse effects caused by serum eye drops. These results suggest that autologous serum application is effective in improving the symptoms and signs of severe dry eye.