SUMMARY
This paper intends to contribute to a better understanding of the co-opetition (simultaneous co-operation and competition) process within horizontal networks in small and medium-sized companies, which is a relevant field of study in strategic management. The objective of this investigation is to analyze the key elements characterizing co-opetition within horizontal networks in selected small and medium-size companies based in Rio Grande do Sul state. Its strategy was a multiple case study, in a qualitative survey, using semi-structured in-depth interviews and documental analysis as data collection procedures. Associates and managers of the Agafarma and Redecore networks were interviewed. The data were treated and analyzed using the technique of content analysis. The results show that the key elements of co-opetition identified on the basis of the theoretical background are present in those networks, including (i) trust and reciprocity; (ii) complementarity and commitment; (iii) exchange of experience and learning;(iv) history and identity; (v) adaptability and alignment; (vi) interdependence and equality; (vii) incompatibility and conflicts; (viii) competition and rivalry; (ix) control and standardization; (x) individual and collective performance; and (xi) independence and autonomy. The networks have all these elements in different degrees of intensity, due to their different and specific features, such as size, operation field, period of existence, direct and non-direct competitors, and other aspects. It must be highlighted that the elements linked to the dimension of cooperation are present in the networks more intensely than the elements linked to competition.Key words: horizontal networks of companies, co-operation networks, co-opetition, key elements.