Since 1990, mandatory HIV tests have been administered to each inmate in Taiwan, including drug-using offenders, when they are first incarcerated. Before 2001, no more than ten new infections among injection drug users (IDUs) were reported each year. In the past few years, however, the number of new infections among IDUs has been growing at an alarming rate (Chen and Kuo 2007 Fig. 1 . For Taiwanese IDUs, sharing needles/syringes and heroin diluents are major risk factors (Chen 2005) . After a harm-reduction programme was launched in 2005, the proportion of IDUs infected with HIV declined to 60.5% in 2006 and then dropped dramatically, to 36.7% in 2007 (Table 2) . The role of non-formal education 341