For identification of canker producing fungi in Guilan province, sampling from different locations in summer of 2016 was carried out. Parts of the trunk and branches with symptoms were transfered to the laboratory and the presence of fruiting bodies was investigated for identification. For purification, single spore method was applied on WA 2% and the specimens were grown in suitable culture media at 25 °C. According to the results, three species belonged to Microthia, Lasiodiplodia and Seiridium were identified. In the genus Microthia (from Cryphonectriaceae family) ascostroma is semi-immersed to superficial, pulvinate and orange. Perithecia are spherical to ovoid, 82-145 × 57-62 μm, in groups of 2 to 12, surrounded by a host tissue. Asci are fusiform to cylindrical, with 8 ascospores, 20-35×4-6 μm. Ascospores are hyaline, ellipsoid to fusoid, 6-7.5×1.5-3 μm. Anamorphic stromata is semi-immersed to superficial, orange, uni- to multilocular, often occurring in the same stroma that contains perithecia, 47-75×3-35 μm. Conidiophores are cylindrical with long paraphyses between them and 30-60×1 μm. Conidia are hyaline, cylindrical to ellipsoid, aseptate, 2.5-3×1 μm. In the genus Lasiodiplodia (from Botryosphaeriaceae family) ascomata was not observed. Pycnidia were produced on pine needles on WA within 2–4 weeks. Pycnidia are dark brown to black, covered with dense mycelium, globose, 0.8-1.2× 0.5-0.7 μm. Paraphyses are hyaline, cylindrical, 43-85×2-3 μm. Conidiogenus cell is holoblastic, hyaline, cylindrical, 12-19×2-3 μm. Conidia are ellipsoid to cylindrical, 18-23×8-15 μm, at first white and aseptate, but became dark brown with 1-septate and longitudinal striation after maturation. In the genus Seiridium (from Amphisphaeriaceae family) ascoma was not observed and was associated with canker on Musk willow )Salix aegyptiaca). In this fungus Conidioma are acervular, 0.3-0.5×0.2-0.25 μm. Conidiophores are hyaline, cylindrical, sometimes curved, 11-25×2-3 μm. Paraphyses are hyaline, 40-50×1-2 μm. Conidia are formed terminally, 5-septate, with 4-brown cell and hyaline end cells, 20-31(37)×7-9 μm. The exact identification of these species is under investigation.