Technical Abstract: In 2008 fluorescent bacteria were isolated from bacterial leaf spot symptoms on Italian parsley (Petroselinum crispum) in Ceres, California. These isolates were different from the known bacterial pathogens of parsley in California. To determine the etiology of this disease pathogenicity was evaluated on parsley, celery (Apeum graveolens), and coriander (Coriander sativum). Buffer (0.01 M phosphate, pH 7.0) or bacteria suspended buffer (approximately 108 CFU/ml) were inoculated by spraying until run off. All plants inoculated with bacteria developed leaf spot symptoms. DNA fragment banding patterns of the original eight isolates and the fluorescent reisolates from symptomatic tissue from pathogenicity tests were identical to each other by rep-PCR with BOXA1R primer and differed from Pseudomonas syringae pv. apii, P. syringae pv. coriandricola and P. viridiflava. BLAST was used to compare the 16S rDNA gene sequences from the parsley isolates to those in public databases. The16S rDNA sequences from the parsley isolates were identical to the 16S rDNA sequence of the type strain of Pseudomonas viridiflava. Although rpoD and gyrB sequences of the parsley isolates were most similar to those of P. viridiflava they were not identical. These results indicated that the unknown pathogen isolated from parsley was related to but not identical to P. viridiflava. Further taxonomic work is needed to determine if these isolates represent a new species or pathovar of P. viridiflava.