Malignant transformation on any scar tissue is known as Marjolin's ulcer. Most cases of Marjolin's ulcer reported so far occur in post-burn scars but not all ulcers that occur in post-burn scar are malignant.One hundred and forty cases of chronic non-healing ulcers in post-burn scar were included in this prospective observational study. The study was conducted in the Department of Burn and Plastic Surgery Unit of Dhaka Medical College Hospital.Mean age of the patients was 40.63±18.44 with a range from 12 to 75 years. Two third of the patients were male. All patients underwent excision biopsy and coverage with either split thickness skin graft or flap. Histopathological analysis of the resected specimen revealed malignancy in 46 cases and pseudoepitheliomatous hyperplasia in four cases and verruca plantaris in one case. The rest of the cases were chronic non-healing benign ulcers. All 46 cases of Marjolin's ulcer were squamous cell carcinoma with a mean latency period of 26.73 years. The commonest site of chronic ulcer was in the lower extremities (n-80, 57%), and malignancy was also found to be more common there (n-18). The most common type of burn was flame burn (68.57%). The Marjolin's ulcers were significantly larger in size than benign ulcers, and were mostly exophytic or ulcerative in appearance whereas benign ulcers were mostly flat.A non-healing ulcer in a post-burn scar should be addressed promptly because of its potential to develop into a malignant ulcer. Emphasis should be given to early surgical treatment of deep partial to full thickness burns to prevent scar formation, particularly over joints, and thus reduce the risk of development of Marjolin's ulcer.