Abstract: Objective The study was conducted to determine the prevalence of sexually transmitted diseases (STD) in sexcriminals and AIDS related risk behaviors, providing evidence for the improvement of STD and AIDS prevention andinterventions. Methods　A total of 228 female sexual workers and 130 patrons in the asylums/correctional facilities inDongguan city were individually inquired and registered, with each 5 ml blood collected for HIV antibody and syphilisantibody detection. Results　Of all 228 sexual workers, the youngest was aged 16 years. The average age of them was 24.31.The youngest patron was aged 19 years, the average age being 32.97 years. Sex workers below the age of 30 were more than thepatrons of the similar age (sup2/sup = 63.53, IP/I0.01); they were mostly unmarried, whereas the proportion of unmarried patronswere smaller (sup2/sup = 22.83, IP/I0.01). Both sex workers and patrons consisted mostly of migrant people and those at the level ofno more than junior secondary education, accounting for 99.56%, 91.23% and 99.23%, 84.62%, respectively. The proportion ofsexual activities where condoms were not used amounted to 14.62% in patrons and 6.58% in prostitutes, the former beingobviously higher (2=6.22, P0.05). Seven sex workers admitted drug addict, and one had a history of sharing syringes. Atotal of 35 cases were confirmed positive for syphilis antibody testing, the positive rate being 15.35%; 12 positive patronswere found, the positive rate being 9.23%. Two sex workers were found infected by HIV, the infection rate being 0.88%.However, no HIV infected patrons were identified. Conclusion　High infection rates and incidence of STD related riskbehaviors were found in sex criminals, and these risk behaviors were more commonly seen in patrons of brothel. Therefore,AIDS/STD surveillance for sex criminals should be intensified in conjunction with health educa