In summary, the non-formal educational programmes in each country highlight the importance of environmental factors and their predictive ability in modifying HIV prevention behaviours among FSWs in the Philippines and IDUs in Taiwan. The results underscore the importance of developing structural and organizational interventions to prevent HIV/STDs. In addition to improving knowledge, efficacy, and skills related to needle use and safe sexual practices, health workers involved in these non-formal educational activities should work closely with community gatekeepers to create a supportive environment for HIV prevention.