This study evaluates the efficacy of cultural adaptation of a voluntary counseling and testing (VCT) intervention, in increasing condom use and decreasing rates of sexually transmitted diseases (STDs) among a group of female sex workers (FSWs) in Guangxi, China. This intervention is modeled after the "state-of-the-science" VCT program that was developed and evaluated by the Center for Disease Control and Prevention's Project RESPECT. Four hundred FSWs were assigned to either an intervention group receiving the VCT intervention or a control group receiving standard of care STD testing and treatment. Data were collected at baseline and 6 months postintervention. Outcome measures included HIV/STD related knowledge and perceptions, condom use, and history of STDs. Five common STDs were screened and tested through clinical examination and laboratory testing to serve as biomarkers. After controlling for potential confounders and baseline differences, the VCT intervention group was significantly higher than the control group in HIV/STD related knowledge (p < .0001) and consistent condom use with clients (odds ration [OR] = 2.23; 95% confidence interval [CI] = 1.26-3.96) at 6 months follow-up. In addition, the intervention group had a significantly lower infection rate of STDs than the control group at follow-up (OR = 0.44; 95% CI = 0.24-0.80). This quasi-experimental trial provides evidence that the brief VCT intervention, through appropriate cultural adaptation, can be efficacious in increasing condom use and reducing STD infection rate among FSWs in China.