Monolithic Interconnected Modules (MIMs) are high voltage, low current devices for the use under very high light intensities. For the first time GaAs-based MIMs are now available to be tested in terrestrial concentrator systems. We report on the development of GaAs MIMs with 30.3 V open circuit voltage and a maximum efficiency of 22.0%. The MIMs are designed to operate at a concentration ratio of 1000 suns. A novel type of bypass diode is integrated into each MIM segment to protect against reverse voltages (patent pending). 24 MIM chips are assembled on a water-cooled heat sink to form a compact 10 cmtimes10 cm receiver. The first fully functional prototype is presented in this paper