The paper discusses and analyzes the scientific search service Google Scholar (GS). The focus is on an exploratory study which investigates the coverage of scientific serials in GS. The study shows deficiencies in the coverage and up-to-dateness of the GS index. Furthermore, the study points up which Web servers are the most important data providers for this search service and which information sources are highly represented. We can show that there is a relatively large gap in Google Scholars coverage of German literature as well as weaknesses in the accessibility of Open Access content. Keywords: Search engines, Digital libraries, Worldwide Web, Serials, Electronic journals