Contaminating bovine viral diarrhea (BVD) virus in cell cultures and in fetal bovine serum (FBS) is a well recognized problem. This study describes a direct peroxidase (DP) labeled primary antibody method for detection of pestivirus antigens in cell culture that is simple and reliable. Using this method, most bovine and porcine cell cultures, a cat lung, four mosquito and two monkey cell cultures were found contaminated with BVD virus. The rodent and human cell cultures tested were negative by this method for BVD virus.