Doctoral thesisAntibiotics resistance is a global concern that presents a major threat to veterinary public health as it reduces the effectiveness of antibiotic treatment in livestock and people. Many studies on antibiotics resistance have been based mainly on microbiology, biomedical and veterinary sciences in laboratory test with little attention paid to social aspects. Based on pastoralist communities in Ngorongoro District in Tanzania, the study examined how supply systems and social networks determine the access and use of antibiotics and their implications on antibiotics resistance. Specifically, the study sought to map out and examine how supply systems and social networks determine the access and use of antibiotics and to examine the implications of supply systems and social networks on antibiotics resistance. The study used both quantitative and qualitative approaches involving survey, key informant interview, focus group discussion; participatory wealth ranking and observation methods. A sample size of 221 respondents and 21 key informants were involved in the study. Quantitative data were analysed using statistical package for social sciences computer software version 20. Qualitative data were analysed using content analysis. The findings revealed that supply systems have failed to provide adequate quality antibiotics and veterinary experts to impart proper knowledge, information, services and monitoring as well as regulatory control mechanisms for the distribution channel of antibiotics from the various sources to end users. This has forced end users to resort to strategies such as sharing antibiotics and knowledge on use of antibiotics. Among the important actors in social networks who determine access to and use of antibiotics include neighbours, friends, relatives, interest groups and traditional dealers. These actors are connected with social ties based on trust and reciprocity. However, they have limited knowledge on antibiotics handling and administration hence resulting into misuse of the drugs. This lack of knowledge has implications on antibiotics resistance. It is concluded that supply systems is associated with inadequate quality antibiotics, limited number of experts and limited knowledge of users of antibiotics. All these contribute to problem of antibiotics resistance. Therefore, social aspects are equally important in explaining antibiotics problem in livestock. It is therefore recommended that there should be capacity building to those who are involved in the supply systems and users on the proper access and use of antibiotics. Also, awareness creation to the public on the problem of antibiotics resistance should be part and parcel of the design and implementation of the livestock policy planning and interventions.