The goal of this research is to analyze and understand the critical factors to take into account when developing policies oriented to create and sustain loyalty in customers. The scope of the research is Small and Medium Sized Enterprises (SME’ s) mainly those small ones, although some medium sized have been analyzed as well. All the analyzed companies operate in the B2B sector and are based in the geographical area of Catalunya (Spain), making the research very specific and specialized. After a deep analysis of the literature review published mainly in the last 15 years, it has been designed a set of 8 case studies which cover several research techniques like personal interviews with the managers, observation, data collection, surveys and experimentation using simulation software tools. Out of the total 8 companies, 6 of them are small, (between 10 and 49 employees), and 2 of them are medium sized ( between 50 and 500 employees). The conclusions of the research are expressed into the final “Model of Customer Loyalty Drivers applied to SME’s in a B2B environment”.