Bacteriologic, mycologic, and serologic investigations of cows and calves and three experiments with rabbits were carried out to shed light on the bacteriology and mycology of the intrauterine infections in cows. The following organisms were isolated from the investigated cows that exhibited disturbances in their reproduction, and had abortions, or gave birth to calves that were affected with diseases or died: Escherichia coli (17.84%), association of bacteria (7.64%); Vibrio genitalis (3.86%); Streptococcus sp. (2.78%); moulds (2.54%); Staphylococcus aureus (2.20%); Proteus sp. (1.62%); Staphylococcus epidermidis (1.39%); Pseudomonas aeruginosa (1.39%); Pasteurella multocida (0.11%). The serologic investigation of a total of 231 blood samples from cows that miscarried, gave birth to dead calves, or failed to conceive revealed that in 15.58 per cent there was vibriosis, and in 6.06 per cent--leptospirosis. Demonstrated was the etiologic link between cows with reproductive disturbances and diseased calves with regard to vibriosis and leptospirosis. The tests with rabbits were indicative of bacterial carriers (with special reference to the genitalia) up to the 60th day following infection. There were abortions, sterility, and death cases and the birth of unviable bunnies in the case of reproduced coital infections with Escherichia coli and Pseudomonas aeruginosa.