Investigate clinical features and tests of pyoderma gangrenosum at National hospital of Dermatology and Venereology (NHDV). Method: A restrospective, descriptive cross-sectional study was performed in 17 pyoderma gangrenosum patients at National hospital of Dermatology and Venereology (NHDV) from 1st Jannuary 2007 to 1 st Jannuaruy 2013. Results: Pyoderma gangrenosum was more common in male with 82.35 percent. Patients who are over 50 years old accounted for 58.82 percent of all affected patients and non of them are under 20 years old. There was 82.35 percent of the patients are from rural areas. Regaring to clinical features, 100 percent of the patients having necrotic ulcerations and 41.18 percent of cases among them have pus on the lesions. Bullous lesions accounted for 35.29 percent. There was 76.47 percent of the patients having lesions with purple boder. Common sites of lesions are in legs of 64.72 percent, less common sites are in back, anal areas and other scattered sites which shared the same rate of 11.76 percent. Pain at skin lesions was the main subjective complaint which was noted in 100 percent of the patients. There was 94.12 percent of the cases responding well to treatment with corticoid. Relating to tests, there was 47.86 percent of the cases having an increase in number of while blood cells in their complete blood counts, this rate was 52.94 percent for polymorphonuclear neutrophils. Bacterial culture was negative in 88.24 percent. 100 percent of histopathology was non specific inflammation. Conclusions: Pyoderma gangrenosum is an uncommon skin disease, the diagnosis depends mainly on clinical symptoms and a good recovery after treatment with corticoid.