Large positive magnetoresistance of Bi nanoparticles, comparable with that in Bi thin film or nanowire arrays, has been shown here. Bi nanoparticles of average particle diameters of 50 or 100 nm were fabricated and giant magnetoresistance was observed near room temperature. In a field of 8 T, MR in 100 nm Bi nanoparticles, which is 230% at 10 K or 80% at 300 K, is larger than that in 50 nm Bi nanopaticles, which is 100% at 10 K or 40% at 300 K. The MR effect in bismuth may be related with its layer structure. (C) 2003 Elsevier Ltd. All rights reserved.