Mycotic infection was diagnosed in 6.8% of 6,858 cases of bovine abortion and stillbirth examined during a 9-year period. Aspergilli were associated with approximately 5% of all abortion cases and 71% of 446 cases that were cultured for fungi and diagnosed as mycotic abortion. Aspergillus fumigatus was the most frequent isolate (62%), followed by A. terreus (6.7%), Emericella (Aspergillus) nidulans (3.0%), A. flavus (2.9%), and E. rugulosus (less than 1.0%). Zygomycetes (Absidia, Mortierella, Rhizomucor, Rhizopus) accounted for 21% of the cases. Pseudallescheria boydii and yeasts (Candida, Torulopsis) were each identified in 2% of the cases. Fungi that uncommonly cause infection accounted for 2% of the cases and included Curvularia geniculata, Exophilia jeanselmei, Hendersonula toruloidea, Lecythosphora hoffmannii, Talaromyces flavus var. flavus (Penicillium vermiculatus), T. (Penicillium) thermophilus, and Wangiella dermatitidis. About 10% of the mycotic cases were mixed fungal infections involving A. fumigatus (87%), A. flavus (12.5%), or E. nidulans (12.5%) coexisting with Absidia corymbifera (72%), Rhizomucor pusillus (4.3%), or Rhizopus arrhizus (4.3%). In each mixed infection, both septate and nonseptate hyphae were observed in placental tissues. Twelve percent of the mycotic abortion cases were diagnosed by histologic examination alone because isolation attempts were negative or only formalin-preserved tissues were available.