[Characteristics and the estimated size of men who have sex with men in different venues of one city].

Objective: To study the features, safe sex behavior and the size of men who have sex with men (MSM) population in actual and virtual venues in one city.

Methods: We carried out a cross-sectional study in actual and virtual venues, using the Estimated Size of Population from a Single Sample (LMS method) to estimate the size of MSM population.

Results: Most MSM in actual venues were 24 - 43 year olds and had received high school education, whereas in virtual venues, the majority of this population were younger than 29 years old and had higher education, including some college students. The awareness of AIDS of the two groups from different venues showed no statistically significant difference, neither the safe sex behaviors. Proportions of the MSM population in actual and virtual venues were 21.22% (16 383, 95%CI: 11 514 - 21 252) and 78.78% (60 830, 95%CI: 57 327 - 64 329), respectively. After adjusting the overlapping part of the MSM from both venues, the total number was between 60 830 and 77 213, constituting a proportion of 5.03% - 6.38% in the sexually active male population (15 - 64 year olds) in this city.

Conclusion: The size of the MSM population was large but the characteristics were different in the actual or virtual venues. As most MSM preferred going to the virtual venues, intervention program on AIDS-specific strategy in this area, in particular dealing with the Internet, should be strengthened.