The pathogenicity ofBeauveria bassiana(Balsamo) Vuillemin andPaecilomyces fumosoroseus(Wize) Brown&Smith to the onion maggot,Delia antiqua(Meigen), was studied at 50% RH in the laboratory. Conidiospores ofP. fumosoroseussprayed on puparia of the onion maggot at the concentration 1 × 108ml−1(=4 × 105cm−2) increased pupal mortality to 47.5% as compared with 6.6% in the controls. There was no latent effect on adults that emerged from treated puparia. Spores ofB. bassianasprayed at the same concentration had no effect on pupal and adult mortality. Sixteen additional species of fungi were recovered from test puparia during reisolation ofB. bassianaandP. fumosoroseus. Species from the generaAspergillus,Fusarium,Geotrichum,Penicillium,Mucor, andScopulariopsiswere isolated,A. clavatusDesmazières being the most common among them. This fungus grew faster than the entomopathogens in vitro and might have inhibited their action in vivo.