The biochemical characteristics of infectious bovine rhinotracheitis virus (Bovine herpes-virus 1, BHV 1) are reviewed: description of the virion particle and virus purification, analysis of structural and non structural proteins, nucleic acid properties, restriction endonuclease analysis of the viral DNA. The authors emphasize the biochemical methods able to insure a better understanding of the molecular epidemiology of BHV 1 and of its latency; also to develop biochemical weapons against the infection.