Hansfordia sp. was found parasitizing papaya black rust and tomato leaf mold in the field in Puerto Rico and on Cladosporium cladosporioides in the laboratory. The fungus was first detected on the margins of lesions spreading towards the lesions' centers. Black rust and leaf mold colonies became completely covered and decolorized by the hyperparasite. Growth of Hansfordia sp. was greatest on black rust and least on C. cladosporioides. The fungus did not grow on corn meal agar but grew and sporulated on malt yeast and potato dextrose agars. Although Hansfordia did not grow on corn meal agar alone, it did grow sparingly on C. cladosporioides growing on corn meal agar. Hansfordia sp. reduced radial growth of C. cladosporioides 25,10, and 0% on potato dextrose, corn meal and malt yeast agars, respectively. On potato dextrose agar, parasitism of Hansfordia sp. on C. cladosporioides reduced production of viable conidia by over 90%. Besides having potential importance in the biological control of leaf blights by dematiaceous fungi, this Hansfordia sp. may be an important tool in studying fungal melanin degradation.