An integrated approach, based on the analysis of both molecular and morphological characters, has led to the unambiguous detection and identification of the rust hyperparasiteCladosporium tenuissimumfrom aeciospores of the two-needle pine rust fungiCronartium flaccidumandPeridermium pini.Cladosporium tenuissimumwas first detected from contaminated field-collected rust spores using the polymerase chain reaction (PCR) method. The similar-sized amplified DNA of the parasite was then separated from rust DNA using electrophoretic migration, reamplified separately with the nested PCR, and sequenced. Sequence comparison in the data banks enabled the hyperparasite to be recognised as a species ofCladosporium. Molecular detection was followed by conventional identification, obtained by plating rust spores on potato dextrose agar, a selective medium for rusts, since they are unable to grow on such a common substrate, and isolating the hyperparasite in pure culture. It was subsequently identified asC. tenuissimum. Traditional identification would not have been possible without guidance from the molecular data, which focused attention on the mycoparasite. Macro- and micro-scopic features of colonies are also given to help with future identification on spore sources from other geographical areas and, if this should occur, future identification on other rusts.Key words: mycoparasitism, PCR detection, traditional detection,Cladosporium tenuissimum,Cronartium flaccidum,Peridermium pini.