The insight that the Holy Spirit plays a decisive role in Luke-Acts is not a new one. Works up until now have however either not taken into consideration all instances of the Holy Spirit within Luke-Acts, or have dealt with thematic limitations from the outset. In contrast, Heidrun Gunkel offers a comprehensive examination of the subject, illustrating how Luke portrays the Holy Spirit's diverse functions and effects. Like stones in a mosaic, each finding slots into place to reveal an overall picture of Luke's pneumatology and serves to underline that the Holy Spirit is an important building block in his theology. On this basis, the author examines how Luke uses his formative perceptions of the Holy Spirit, set against a backdrop of Old Testament, Jewish and Hellenistic perspectives, in order to make his message intelligible to both Jews and Greeks alike.