A total of 457 nasal swab specimens from cases of respiratory disease in 2 feed lots were evaluated for the detection of bovine herpesvirus Type 1 (BHV-1) by ELISA. Thirty-three were found to be positive for BHV-1 by the recovery of infectious virus and 21 of these were positive by ELISA, yielding a sensitivity of 64%. Fifteen other virus isolations were made and included bovine viral diarrhea viruses, rhinoviruses and parainfluenza Type 3 viruses; none of these cases were positive with the BHV-1 ELISA. Specificity of the ELISA was 100%. Eighty percent of the specimens with BHV-1 titers greater than 10(5) TCID50 were detected by ELISA; the median amount of virus in positive specimens that were detected by ELISA was 7 X 10(5) TCID50 and the median amount of virus in specimens not detected was 1.5 X 10(4) TCID50. BHV-1 infection was most frequently diagnosed in feedlot cattle that had been in the feedlot for 40-80 days. Approximately half of the infected cattle were carrying virus-neutralizing antibodies in their serum.