In the R&D and innovation related literature, the term “R&D performing enterprise” is not a definitive one. Various terms are used and numerous classifications have been developed based on institutional sectors, ownership, affiliation, main economic activity, size, geographical location, R&D capability and intensity, R&D regularity and other characteristics. The aim of this study was, firstly, to summarise the current state of understanding of R&D performing organisations; and, secondly, to establish a theoretical framework for the author’s PhD project investigating factors affecting long-term survival and growth of small and medium-sized R&D performing enterprises.