This paper aimed to study the set of plastics manufacturers located in the city of São Caetano do Sul, Brazil, in particular the group most heavily concentrated in San Antonio and Central neighborhoods, checking to what extent this set fits the concept of Industrial Cluster, defined by Porter (1998) and other authors. The study sought to replicate the method used was quantitative research modeled by Bell (2005), which was adapted, resulting in qualitative research. The results based on qualitative research indicate that companies remain very tenuous relationship, considering the managerial and institutional networks, which indicates they do not constitute a cluster, despite the concentration. By comparing the theoretical frameworks available that deal with the creation of knowledge in the environment of cooperation and trust in Cooperation Networks, LPA or clusters with the situation found in the group of industries studied, it appears that companies probably do not take advantages of this agglomeration. The results indicate that it is important that the other actors in the region (public agencies, universities and development banks) to implement an agenda aimed at developing the skills of these clusters and its actors.