The expression kinetics of an essential trans-regulatory protein, ICP27, from herpes simplex virus type 1 correspond to that of an immediate-early gene whose expression increases rapidly upon infection and then decreases as of 7 hr postinfection. In contrast, here we report that the bovine herpesvirus type 1 (BHV-1) homolog BICP27, a 50-kDa protein, is expressed as an early gene. Both the transcript and protein accumulated gradually reaching peak levels at approximately 12 hr postinfection, after which point steady state levels were maintained up to 24 hr. Thus the expression profiles of ICP27 and BICP27 are significantly different, suggesting that they may possess different functions.