Description: To correlate the clinical course of mycoplasma mastitis with its immune response, right mammary glands of 15 lactating goats were inoculating with 1010 colony-forming units (cfu) of Mycoplasma agalactiae (Ma). Before sacrificing the animals at 5, 15 or 45 days post-inoculation (dpi), blood Ma antibody titres and milk mycoplasma colony and somatic cell counts were monitored. Ma colonised the mammary gland and milk counts increased to over 1012 cfu/ml within 5 dpi. During this period, an innate immune response involving neutrophils and macrophages was observed, and Ma antigen appeared in the degenerated acinar epithelium. From 7 dpi, a specific antibody response coincided with reduced viable mycoplasmas in milk. The humoral immune response was limited; by 37 dpi, all animals scored negative for anti-Ma antibodies, and around 108 cfu/ml were shed. Results indicate an early immune response to Ma inoculation unable to control mycoplasmal invasion. An ensuing humoral response, despite reducing the mycoplasma burden, leads to chronic, persistent infection