To determine the effects of pathogen exposure to Enteromyxum leei on head kidney gene expression. Keywords: confinement, cortisol, stress response, time course, microarray 30 head kidney samples - Thirty slides were hybridised using a reference design. Three groups (control, infected and non-infected) were compared using five individual fish in each group. Each sample was hybridised twice - the second being a dye-swap of the first.