Susceptibility ofDelia antiqua(Meigen) to 11 isolates of entomopathogenic hyphomycetous fungi was studied in the laboratory. Newly formed pupae were sprayed directly with four concentrations of aqueous spore suspensions ofBeauveria bassiana(Balsamo) Vuillemin (three isolates),Metarhizium anisopliae(Metschnikoff) Sorokin (three isolates), and one isolate each ofMetarhizium flavovirideGams&Rozsypal,Nomuraea rileyi(Farlow) Samson,Paecilomyces farinosus(Dickson ex Fries) Brown&Smith,Paecilomyces fumosoroseus(Wize) Brown&Smith, andTolypocladium cylindrosporumGams. Pupae were generally not susceptible to mycoses but deferred mortality was observed in adults that emerged from puparia treated with nine of the fungal isolates.N. rileyi5 andM. anisopliae120 did not induce mycosis in adult flies. Mortality due to the other isolates ranged from<5% (T. cylindrosporumat 4 × 105blastospores ml−1) to 75% forP. farinosusandP. fumosoroseus(4 × 105conidia ml−1). The threeBeauveriawere moderately pathogenic at all four concentrations tested. Sporulation occurred on 56% of adults infected withM. anisopliae71 and on 17% of those infected withM. flavoviride(4 × 105conidia ml−1). Significant differences were thus found between isolates with regard to their ability to infect emerging adults, but dose-level differences for a given isolate were generally not significant. Overall, toxicity appeared to have been more evident than pathogenicity and resulted in reduction in numbers of viable and fertile adults that emerged from puparia treated with nine of the isolates.P. farinosus46 andP. fumosoroseus45 (LD50's in the range of 103conidia cm−2) are promising candidates for the control ofD. antiqua.