Purpose: The purpose of this paper is to identify the key roles embedded in the informal organizational structure (informal networks) and to outline their contribution in the companies' performance. A major objective of the research is to find and characterize a new key informal role that synthesises problem solving, expertise, and accessibility characteristics. Design/methodology/approach: A framework for an in-depth informal structure analysis based on social network analysis (SNA) methodology is structured and applied in a case study of a knowledge-based enterprise operating in the information systems industry. Findings: The paper identifies and characterizes the key informal roles (namely opinion leaders, central connectors, bottlenecks, experts, consultants, or helpful people) and a new one, called "pilus prior" (first lancer) that synthesises problem solving, expertise, and accessibility characteristics. Research limitations/implications: Future research will move through the enlargement of the sample that will allow a better generalization of the results and the development of a model to quantitatively evaluate the performances of individuals recognized as informal leaders. Practical implications: The proposed framework has a general applicability and can be a valuable tool for an in-depth organizational analysis based on SNA methodology. Consequently, some directions are provided to increase cooperation and knowledge sharing flows inside the company and to align the formal organizational processes to the informal one. Originality/value: The results of the research have been achieved by using an original approach, the joint analysis of three informal networks. The case suggests that "pilus priors" are the informal emerging leaders in the company who outperform their colleagues. (Contains 5 tables and 7 figures.)