Two powdery mildew species have been collected from Iran. For the first time, Erysiphe magnifica on Magnolia sp. was identified from Iran based on morphological and molecular characteristics. Erysiphe corylacearum was collected for the second time in the country and reported for the first time from Guilan province. There are some polymorphisms in ITS-rDNA sequences of E. corylacearum between Iranian and GenBank sequences. This polymorphism is worth of attention for better understanding of the taxonomy of the species and role of ITS sequences for species delimitation. The ITS sequence of the Iranian specimen of E. magnifica was 100% identical to four ITS sequences of E. magnifica in GenBank. Morphologically, E. magnifica was characterized by curved, flexuous and relatively long foot cells, whereas, foot-cells of conidiophores have been reported in the literature as relatively short. According to these observations, it is recommended to check as many characters as possible for identification of morphologically and molecularly closely related species.