Male sex workers are known as a high risk group of STIs infections however the awareness of this group was limited. Study describes the proportion and some factors relating to STIs infection among male sex workers in Hanoi. Result shows the average age of the study participants was 22 + or - 3.4, 78 percent of them were born in provinces. The first time of commercial sex was mostly at the age of 20 + or - 3.1. Accounting for 65 percent of the subjects made money by selling sex in the last 30 days. The prevalence of STIs infections among male sex workers was 46.4 percent. Some factors such as the education level, unsafe sex with foreign clients in the last time, the number of clients and the average number of commercial sex in the last 30 days were the factors associated with STIs infections.