Dissertation (MSc Nursing Mental Health)Background: Injecting drug use has created a major international public health problem where on average 6 million people are injecting drugs worldwide. This study aimed to explore the potential of bridging the HIV infection from injection drug users (IDUs) through sexual networks to the general population in Zanzibar. Seek to understand the interplay between injection drug use, sexual behavior and the epidemiological shift in the transmission of HIV infection between key population and the general population, thereby contribute to reducing HIV epidemics in both sides. Objective: The role of sexual networks in bridging HIV infection between injection drug users to the general population in Zanzibar. Methods: Quantitative cross-sectional study design was used whereby data was collected from1308 adults of all sex with age ranging from 18 to 64 years who are injection drug in Zanzibar. The data collection method was by the use of self– administered questionnaires. Results: Participants who had sexual debut below 18year were had a high risk in sexual network to the general population OR= (95% CI) 1.353(0.999, 1.833) p<0.05, most of the participants that practice steady partners were at risk in sexual network OR= (95% CI) 1.407(1.047, 1.893) and p <0.05. Marital status was also the main factor for IDU whereby participants who were reported to be separated, widow or divorced were at less risk of IDU sexual network compared to those who were married 95%CI (0.347,0.753), and P< 0.05). Type of drug used was also the determinant for IDU sexual network whereby participants that reported to take amphetamine were less likely to be in sexual network compared to those taking heroin OR 0.279, 95%CI (0.138, 0.564) and P < 0.05) vi Conclusion: We found evidence to support the hypothesis that sexual networks are responsible for bridging HIV infection among injection drug users and the general population in Zanzibar. Recommendation: In order to control this problem, further efforts should focus mainly on controlling the use of heroin, preventing sexual debuts below 18 and giving sexual education among married groups. Establishment of awareness and ongoing risk reduction programs of IDUs and community how to live in safety also, sexual practice in an effort to achieve the goal of zero new infection due to the sexual network.