The HIV epidemics in some areas of Yunnan Province, southwestern China, are close to becoming generalized, demanding the need for a better understanding of sexually transmitted disease (STD) and heterosexual HIV risk. While female heterosexual risk is captured by sentinel surveillance, less is known about clients of commercial sex workers and other subsets of men at increased risk of STD/HIV. A convenience sample of 232 miners in townships of Yunnan Province completed a questionnaire and provided specimens for STD/HIV testing. Relative prevalences of HIV, gonorrhea, and chlamydia among sexually experienced miners surveyed were 0.5% (1/182), 0.5% (1/182), and 9.3% (17/182), respectively. Chlamydia seropositivity was significantly associated with receiving less education (p = 0.03). Among all respondents, 9.4% admitted to purchasing sex, 82.9% had not used a condom in the last 6 months, and substantial gaps in knowledge about STD/HIV were apparent. Because preventing heterosexual spread of HIV is crucial in this area of China to prevent a generalized epidemic, better understanding and designing low literacy interventions targeted at sex worker clients and similar subsets of high-risk migrants may be warranted.