Recent studies show that many organizations struggle to implement Software Process Improvement (SPI) based on process models and standards mainly because of incapacity to overcome critical barriers, such as lack of motivation and higher management support. The accurate understanding of the social-cultural context where SPI is undertaken can facilitate the development of more efficient SPI implementation strategies aiming to overcome those difficulties. The objective of this work is to present a Grounded Theory based study conducted to investigate SPI implementation initiatives in the perspective of consultants of SPI consultancy organizations. The main product of this study is a theoretical framework that tries and explains the phenomenon associated to the success of SPI implementation initiatives.