Pyoderma gangrenosum is a rare, destructive ulcerative condition of the skin. The painful ulcers may occur spontaneously, or result from a minor injury or surgery. The clinical presentation can mimic a necrotizing bacterial infection; however, no micro-organisms can be cultured from the skin lesions and the ulcers fail to respond to antibiotic therapy. Surgical interventions can aggravate the disease process. We describe 2 patients, a 22-year-old woman and a 45-year-old woman, with ulcerative wound abnormalities after breast surgery. After failure of antibiotic therapy and standard wound care, tissue biopsy of the wounds confirmed the clinical diagnosis 'pyoderma gangrenosum'. Wound healing began after systemic steroid treatment. Delays in diagnosis and treatment of pyoderma gangrenosum may result in extensive ulceration and scarring. It is, therefore, important to recognise the characteristic clinical features at an early stage and to start appropriate treatment immediately.