The Galileo System Test Bed (GSTB) represents an integral part of the Galileo Design Development and Validation in order to mitigate the associated development risks. The GSTB is implemented in two experimentation phases – the first one currently on-going using GPS observable (so called GSTB-V1) and the second one using the navigation signals transmitted from Galileo Experimental Satellites (so called GSTB-V2) to be launched in 2005. The development of the GSTB-V1 has been completed early 2004. It consists of a worldwide network of stations collecting high quality GPS observables at 1 Hz, an Experimental Precision Timing Station, located at IEN Time Laboratory, providing the reference time scale steered to UTC/TAI, and a Processing Center located at ESA ESTEC for the generation of navigation and integrity core products based on Galileo-like algorithms. The paper presents the experimentation results, assessing feasibility of some of the important assumptions and performance objectives of the final Galileo system in a realistic environment, for the following fields: Experimental Galileo System Time (E-GST) and steering to UTC/TAI Orbit Determination and Time Synchronization (OD&TS) and Signal In Space Accuracy (SISA) Integrity computation. The timing, navigation and integrity core products are available to external users through the ESA web site (http://www.gstb-v1.esa.int/).