Abstract. A portion of the Intergenic Spacer (IGS) of the ribosomal RNA operon of 74 isolates of 11 Armillaria species from Europe and North America was amplified using the polymerase chain reaction (PCR). Amplifications were made from scrapes of living mycelium without DNA extraction. AluI digests of the amplified product were electrophoresed in agarose and stained with ethidium bromide. With few exceptions, each taxon had a unique combination of restriction fragments. Most taxa had a single AluI pattern, but two restriction patterns were seen among isolates of A. borealis, A. cepistipes, A. gallica, A. tabescens, and A. mellea. Armillaria ostoyae, A. gemina, one of the A. borealis types, and one of the A. cepistipes types had identical sizes of AluI fragments, but each of these taxa could be distinguished by their polymorphisms after restriction with the enzymes NdeI, BsmI, or HindII. European isolates of A. gallica had a distinct AluI restriction pattern, but North American isolates of this species had a restriction pattern identical to A. calvescens. IGS amplification products were obtained from 8-year-old spore prints and dried basidiomes, as well as fresh wood decay without DNA extraction. The technique allows for identification from decayed wood, basidiomes or mycelia of these Armillaria species in a single day.