Since Field programmable gate arrays (FPGAs) are reprogrammable, faults in them can be easily toleruted once fault sites are located. Previous researches on diagnosis of FPGAs mainly deal with faulty logic block. In this paper we present a method for the testing and diagnosis of faults in the interconnect structures of FPGAs. A predefined set of tests that can locate all single faults and many multiple faults is presented. 01her multiple faults can be located with an adaptive test set. This work, combined with previous works on the diagnosis of faulty logic blocks in FPGAs, make.i it possible to utilize FPGAs withfaults.