4th February 2012 was the world cancer day. It is a day created to create more awareness among public regarding this spreading menace to health around the world. While most of the infectious contagious diseases have been controlled in the developed western countries, still much sickness and deaths   occur due to cancers. The underdeveloped countries are also recording high number of cancer cases. The difference between the two lies in accessibility of public to health care services and affordability of treatment options.  There are number of risk factors which have now been proved to be directly linked to different types of cancers. For example tobacco smoking is a known risk factor for causing lung cancer. Alcohol predisposes to liver cancer. A carcinogen is defined as a substance which is directly involved in causing cancer. Some carcinogens occur naturally. A fungus like Aspergillus flavus (growing on stored grains, nuts and peanut butter) is a classic example of a naturally occurring carcinogen.  Viruses like Epstein bar virus, HPV (human papilloma virus), e.t.c. cause different types of cancers in human beings. HIV makes one more susceptible to develop various types of cancers. There are large number of chemicals present in different substances used in different ways or to which people are exposed, are carcinogenic, i.e. cancer producing.Workers exposed to asbestos are known to develop lung cancer. Similarly lead is a risk factor for causing bladder cancer. Exposure to radiation beyond a safe limit results in cancer. We are exposed to a big number of known and unknown carcinogens unknowingly. Aldehydes and polyvinylchloride involved in manufacturing plastics are carcinogenic. Chemicals present in deodorants and air conditioners in cars, preservatives, colouring and flavouring agents in processed food items, e.t.c. expose one to the risk of cancer. Cancer if detected in the early stages is definitely curable and improves both the longevity and quality of life of an individual. But once it grows in size and spreads to other body parts, curative definite treatment becomes difficult. One becomes sick and can also die early. Therefore it is important that one becomes aware of cancers and on the slightest suspicion of cancer gets himself tested. Unexplained loss of appetite and weight in a person should raise the doubt of cancer. This is more so when all possible investigations reveal no infection. Persistent chronic cough, chest pain, with no response to antibiotics and palliative treatment is a feature of lung cancer.  A person developing chronic constipation or diarrhoea, for which no other cause is detected by investigations, should be screened for colon cancer.Persistent or indolent ulcers in the mouth or anywhere in the body and increase in the size of an ulcer indicate that the ulcer is malignant. Similarly a hard swelling anywhere in the body externally or internally, sudden increase in size and contour of a swelling suggest it to be malignant. People need to be aware of these tell tale signs of cancer. Even if there is a doubt, one should get the tests done. Definitive diagnosis of malignancy is done by means of biopsy. In this a piece of tissue is taken from the affected site and examined for malignant cells under the microscope. In the early stages, treatment is done by surgical removal of the cancerous lesion. Along with it, the surrounding tissues or even the complete organ is removed if needed. But in advanced cases, only symptomatic treatment remains possible. Chemotherapy and or radiotherapy are used to destroy the rapidly multiplying malignant cells. Both these procedures are painful and have multiple side effects.Best option remains to prevent cancers. This is possible by adopting a healthy life style.Avoiding junk food helps in preventing cancer along with preventing allergies and obesity. Persons exposed to harmful chemicals in industries should be provided with protective wear by their employers. They should be counselled about cancer. If they develop cancer, it should be detected and treated at the earliest.The ban on polythene by Government of Rwanda is appreciable as it minimizes the risk of cancer in the society.Mass and individual awareness regarding cancer will definitely help in diminishing its prevalence.  Specialist internal medicine