Technical Abstract: Guava (Psidium guajava L.), one of the most widely grown plants in the tropics, is very susceptible to disease which can decrease its marketability. Leaf and fruit spot diseases commonly occur on guava grown in Hawaii. A disease survey was conducted on more than 50 accessions grown at the USDA/ARS Tropical Plant Genetic Resource and Disease Research Unit in Hilo, Hawaii. The four main fungi isolated from leaves and fruit were Pestalotiopsis, Colletotrichum, Mucor and Guignardia. Disease symptoms of these fungi were visible on leaves without fruit present, and on the skin of young fruits (pinhead size) which progressed as fruits matured. The highest disease incidence by far (>85%) was for Pestalotiopsis spp. The main diagnostic symptoms were grey/light brown lesions surrounded by dark brown borders on leaves and brown, raised, corky, necrotic lesions on the exocarp of fruit. The Pestalotiopsis spp. were isolated, identified and characterized. Pathogenicity was demonstrated on wound-inoculated fruit and leaves by fulfilling Koch’s postulates. Potential sources of host resistance were identified in the germplasm. The importance of Pestalotiopsis as a guava pathogen and its cross-infection potential are discussed.