The pathogenicity of 32 fungal isolates from the genera of Beauveria, Verticillium, Paecilomyces, Metarhizium, Mariannaea, and Hirsutella to second-instar tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was tested under laboratory conditions. These isolates originated from various insect hosts and substrates from France, Denmark, Austria, Italy, Turkey, Syria, and the United States. A single exposure concentration (1 × 10⁷ conidia/ml) assay for each isolate was first conducted by immersing the insects in 10 ml of a fungal suspension for 5 s. These were followed by concentration-mortality assays on five of the most pathogenic isolates using four test concentrations ranging from 2 × 10⁴ to 2 × 10⁷ conidia/ml. B. bassiana 726 (Bemisia-passaged GHA strain) was used as a standard for comparison in all of the assays. Among the test isolates, three produced mortality not significantly different from the water control. Mortality ranged from 35 to 98% among the other 29 isolates. The LC₅₀ values of the five most pathogenic isolates ranged from 0.8 to 5.0 × 10⁵ conidia/ml. The LT₅₀ values for these isolates ranged from 6.0 to 6.9, 3.1 to 5.1, and 2.5 to 4.0 d for concentrations of 2 × 10⁵, 2 × 10⁶, and 2 × 10⁷ conidia/ml, respectively. Two strains of B. bassiana (ARSEF 1394, 5665) and one M. anisopliae (ARSEF 3540) were more pathogenic to the nymphs than the standard, having significantly lower LC₅₀ and LT₅₀ values. Our results demonstrated that several genera of entomopathogenic fungi have promise as microbial control agents against L. lineolaris.