The purpose of this study is to evaluate the effectiveness of reducing HIV transmission among sero-discordant couples by applying comprehensive intervention components.

A cluster-randomized controlled trial was carried out in forty counties from 16 cities. The strategy of Social Marketing was applied to influence sero-discordant couples' behavioral changes including safer sexual intercourses, regular HIV testing for the negative partners, antiretroviral therapy initiation.

Inclusion Criteria:

• Couples are required to have a stable relationship and live together in the last 3 months;
• Older than 18 years and younger than 60 years; without regard to CD4 count;
• Open cohort(any newly diagnosed serodiscordant couples who are eligible for treatment will be included during the study period).

Exclusion Criteria:

• Couples are not have a stable relationship or do not live together in the last 3 months;
• Younger than 18 years old.