Knowledge intensive business services (KIBS) are known to play a significant role in innovation systems. Past research has however mostly treated KIBS as a homogenous group; it is now time to understand better the variety that exists among KIBS. In this study, we apply a mix of qualitative and quantitative methods to examine a dataset of 362 UK-based KIBS firms active in three ‘sectors’: architecture and engineering consulting; specialist design; and software and IT consulting. By applying content analysis techniques to information drawn from firms’ websites, we identify each firm's primary ‘knowledge base’, be that analytical, synthetic or symbolic knowledge. We then relate the firms’ primary knowledge base to their engagement in R&D, design, and innovation, and examine how the ‘drivers’ of innovation vary between firms with different primary knowledge bases. The paper thereby contributes to the literature, first by identifying empirically ‘knowledge bases’, then relating these to the variety that exists among KIBS. The paper concludes by highlighting issues for further conceptual, methodological and empirical research.