SUMMARYFresh tissues of the pileal surface and context of 38 species in six genera (159 collections) of the Boletaceae were spot-tested with the following reagents: KOH, NH4OH, FeSO4, catechol, HCl and calcium hypochlorite. The pink to reddish color reaction of fresh pileal context tissues with KOH and NH4OH reagents distinguishSuillusspecies from other Boletaceae tested. The FeSO4tests on fresh pileal context tissues ofSuillusspecies also separate it fromBoletus, but the similarities of reactions forSuillus, Tylopilus pseudoscaber, andLeccinumspecies and the inconsistency of the reaction on manySuillusspecies indicate the need for further study. At the species level, spot tests of fresh pileal-surface tissues with KOH and NH4OH solutions helped to characterizeSuillus lakei, Boletus spadiceusandB. piperatus.Under the microscope, revived pileipellis tissues ofS. lakei, B. spadiceusandB. mirabilisgave reliable diagnostic color reactions as incrusting pigments dissolved from the cell walls in KOH and NH4OH solutions. These microscopical spot tests are useful for determination of unidentified dried collections.