Isolation and purification of biologically active RNA from filamentous fungi is difficult because of the complex cell wall and the high level of polysaccharides which bind to or co-precipitate with RNA. Using benzyl chloride and guanidine thiocyanate, RNA was successfully isolated from Blakeslea trispora in which other RNA extraction methods and commercially available kits failed to deliver suitable results. The RNA isolated by this procedure appears to be relatively pure, as it has a ratio of absorbance at 260/280 nm of 1.8-1.9. The integrity of the RNA was further substantiated by RT-PCR and Northern hybridization, respectively. This procedure should be useful for isolating RNA from other filamentous fungi and, therefore, will serve as an important tool for the molecular analysis of these organisms.