This study was to describe the risk factors of the breast cancers at patients diagnosed and treated at National Cancer Hospital (K hopital) in 2010. The results showed that some risk factors of the breast cancers were passive smoking, the age of first menses, and marital status. The other factors such as active smoking, BMI, history of maternity, family history only reflect minor differences were not significantly. In conclusion, cancerous patients were mainly from 40 to 49 years old (68 percent of total participants). The average age of patients participating in the study was 44.5 + or - 4.3. They live in rural areas and were married and living with their husbands. The following causes could be leading to breast cancer such as passive smoking, the age of first mense and single women.