Diagnostic studies on aborted placentas of cattle usually do not determine any reason for abortions. In this paper, five bovine herpesviruses (BoHVs) and some bacteriological agents were investigated by several methods in 33 aborted bovine placentas. Inclusion bodies, PCR and in situ DNA hybridization proved the presence of BoHV-4 DNA in six (18.18%) tested placentas. Positive DNA hybridization signal localized BoHV-4 DNA to placental epithelial cells macrophages and lymphocytes. By destroying epithelial cells and provoking local immune response BoHV-4 infection may inhibit physiological functions of the placenta during gestation. This finding is a further sign that BoHV-4 plays an active role in reproductive disorders of cattle.