Skin is considered the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold. For a patient to recover from any illness or weakness that affects the skin, he/she requires an accurate diagnosis of his/her the situation. In this paper will present an expert system that quickly diagnosis patient’s condition and propose a suitable solution for the problem. This expert system is designed and implemented in SL5 Object language. This expert system was tested by a group of physician and found to be a useful tool that aids physicians and patients suffering from skin cancer diseases.