The objective of this study was to make a qualitative and quantitative assessment of the vaginal microflora during the estrous cycle of 34 bitches from kennels with and without fertility disorders, in order to study whether any particular bacterial species is isolated more often in the kennels of low fertility status in general or during a specific stage of the estrous cycle. Furthermore, a serological follow-up of CHV1 antibody titers was performed to determine whether seroconversion, as a result of (re)infection or reactivation, occurs during a particular stage of the estrous cycle and, if so, how it affects fertility. The number of bacteria isolated was significantly influenced by the stage of the estrous cycle. Bacterial counts were higher during pro-estrus and estrus. In the individual bitch the flora changed during the estrous cycle but when all samples were compared, no specific bacterial species could be associated with a given stage of the estrous cycle. No significant differences were found between bitches from kennels with and without reproductive disorders. In all but one bitch, the serum-neutralizing (SN) antibody titers to CHV1 did not change during the estrous cycle. In the one bitch that seroconverted, no effect on the fertility status was found. It was concluded that no correlation between the aerobic vaginal bacterial flora and/or CHV1 and fertility could be demonstrated.