A retrospective study of bovine abortions associated with Bacillus licheniformis is described. The material consisted of 2445 bovine abortions submitted for diagnostics from 1986 through 1993. Initially, B. licheniformis had been isolated from 81 cases. Sections of these cases were reexamined microscopically and immunohistochemically by a PAP technique using a primary antibody against B. licheniformis. Of these abortions, 47 were most likely associated with B. licheniformis as tissue lesions with immunostained bacteria were present in these. In the remaining cases the diagnosis may not have been established due to the lack of sufficient materials, or the isolation of the bacterium was considered to be a result of contamination. In four cases concomitant infections with B. licheniformis and bovine virus diarrhoea virus were present. Abortions caused by B. licheniformis were predominantly seen during the winter months and in late pregnancy. The most common lesions were necrotizing placentitis followed by fetal multifocal suppurative bronchopneumonia. Immunohistochemically, B. licheniformis was demonstrated in association with tissue lesions and intracellularly in trophoblasts. The pattern of bacterial isolations, especially from the placenta, lungs, and abomasal contents, combined with the histological findings points to B. licheniformis abortions as being of haematogenous origin with subsequent transplacental spread to the fetus.