In Taiwan, several concerns have arisen about the HRPs, although they are considered an example of good HIV prevention practice. Several studies have shown that HRPs are effective in decreasing HIV prevalence among criminal justice populations Chen 2007, 2008; Chen et al. 2008 ). Lan and Chen (2008) found that after an HRP was conducted in the northern region of Taiwan at the end of 2005, the HIV prevalence decreased from 37.6 to 18.7% in the detention center within 6 months. In contrast, the prevalence rose by 1.4 and 3.7%, respectively in the central and southern regions where no HRPs were conducted during that period. Significant differences were found between these regions in terms of the change in HIV prevalence. Moreover, the HIV antibodypositive rate among returned syringes also decreased significantly, from 18.0 to 9.4% (p \ 0.001) in 2007.