Introduction: Social network analysis quantifies and visualises communication pathways between actors. This thesis focuses on the application of social network analysis methods to explore healthcare worker professional communication and performance by conducting a systematic review and a network study in Ethiopia. Paper 1: The systematic review analysed what social network methods have been used to study professional communication and performance among healthcare providers. Ten databases were searched from 1990 through April 2016, yielding 5,970 articles. There was marked diversity across all six studies meeting our search criteria in terms of research questions, health sector area, patient outcomes and network analysis methods. The paucity of articles, the complete lack of studies in low and middle-income contexts, the limited number in non-tertiary settings and few longitudinal, experimental designs or network interventions present clear research gaps. Paper 2: A cross-sectional, mixed-methods observational network study captured professional advice networks of 160 healthcare workers in eight primary health care units across four regions of Ethiopia. Data included health care worker advice seeking and giving for the provision of antenatal care, childbirth care, postnatal care and newborn care. Adjacency matrices were uploaded into UCINET 6.0 to calculate network metrics. Networks were visualised using NetDraw. Qualitative interviews of 20 purposively selected subjects followed the collection of quantitative network data to interpret and explain network roles and patterns observed. Expanded field notes were analysed using MaxQDA10. Results: Informal, inter-and intra-cadre advice networks existed. Fellow staff were preferred, but not limited to the primary health care unit. Average network-level metrics: density .26 (SD.11), degree centrality .45 (SD.08), distance 1.94 (SD.26), ties 95.63 (SD 35.46), network size 20.25 (SD 3.65). Conclusion: The systematic review found that network methods are underutilised in this area. The subsequent network study in Ethiopia serves to provide foundational information on healthcare worker professional advice networks.