Alternariaspecies are the causal agents of potato and tomato early blight disease. Three species-specific PCR primer sets were designed for Alternaria alternatasensu lato, Alternaria solaniand Alternaria infectoriaidentification. The specificity of primers was confirmed by the absence of amplified products after PCR with DNA of Alternariaspp., other potato and tomato pathogenic fungal species and plant DNA. Constructed primers were applied for the survey of early blight agents on affected potato and tomato leaves collected in different regions of Russia. All three Alternariapathogens were present in blighted leaves alone or in complex (A. alternata+ A. solani, A. infectoria+ A. alternataand A. solani+ A. infectoria). Alternaria alternata(sensu lato) was the most abundant species. It was detected in 50% of tested potato leaves and 41% of tested tomato leaves (alone or in complex). Alternaria solaniwas found in 30 and 35% leaves, respectively. Alternaria infectoriaoccurred in potato and tomato samples occurred at a somewhat lower frequency (13 and 8%, respectively). Using the specific primers, it was possible to exclude the Alternariadisease in some leaves with symptoms similar to early blight.