Bacteriology, somatic cell counts (SCO) and N-acetyl-β-glucosaminidase (NAGase) activity determinations were conducted on milk samples collected from does in three dairy herds with caprine arthritis–encephalitis virus (CAEV) infection. In two herds, CAEV-infected does were more likely to have a subclinical bacterial infection of the udder than CAEV-free does (P < 0·05). Does with CAEV but no bacterial udder infection had significantly greater mean SCO and NAGase activity than CAEV-free does without udder infection (P < 0·01). In two herds, changes in milk SCC and NAGase associated with CAEV infection were similar to those produced by coagulase-negative staphylococcal infections. The findings confirm that indirect indicators of bacterial mastitis infection may have reduced specificity in dairy goat herds with CAEV.