A comparative study was carried out to determine the susceptibility of 5 different cell types to bovine viral diarrhea (BVD) and infectious bovine rhinotracheitis (IBR) viruses. The cell systems used were swine testicle (ST), mink lung (ML), bovine turbinate (BT), porcine kidney (PK15) and equine dermal (ED) cells. For BVD virus, the titers obtained on day 8 post-infection were 10(1.13), 10(3.25), 10(4.13), 10(0.00) and 10(0.00), in ST, ML, BT, PK15 and ED cells, respectively. For the IBR virus, the titers obtained were 10(2.63), 10(8.5), 10(8.38), 10(3.00), and 10(4.63) in ST, ML, BT, PK15 and ED cells, respectively. This indicates, therefore, that BT and ML cells are optimal for the propagation of both BVD and IBR viruses and that ST, PK15, and ED cells are not very sensitive to these viruses.