Abstract The Space Geodetic (Technique) Services of the International Association of Geodesy, in particular the International VLBI Service for Geodesy and Astrometry (IVS), the International Laser Ranging Service (ILRS) and the International GPS Service (IGS) will make major contributions to the proposed Integrated Global Geodetic Observing System (IGGOS) through the provision of time series of parameters which describe the fundamental components of global reference frames, in particular the International Celestial Reference Frame (ICRF) and the International Terrestrial Reference Frame (ITRF), and parameters of the transformation between them (Earth Orientation Parameters (EOP's), nutation, origin and scale). The three techniques VLBI, SLR and GPS are represented by services, which in the last years have taken over the coordination of the supporting components including observation sites, data routing and management, and analysis facilities. Moreover, they have the responsibility for consolidated product delivery by timely provision of high quality time series, with temporal latency in some cases approaching near real time. The results of the different services reflect the distinct characteristics of the technique observables, which are partly similar and partly complementary. Due to the independence and different sensitivity of the techniques, systematic errors between the three techniques can be detected by appropriate combination of the results and to some extent at the level of the observables. Such a procedure will increase the reliability and the consistency of the products in satisfying the requirements of IGGOS. This paper reviews the different techniques with regard to their advantages and indicates sources of systematic errors. It will focus on requirements which have to be fulfilled for the combination of the service-dependent time series and might provide a basis for discussion on future plans in order to evolve the services themselves towards fulfilling the objectives of IGGOS.