The speed of uptake of A. salmonicida into Atlantic salmon depended on the precise route of infection, and was variable among individuals of any group. Following oral and gill uptake, the pathogen was isolated from the kidney and blood. Application via the lateral line, ventral surfaces or flank led to the presence of cells in blood and spleen, but not in the kidney. Uptake via the anus, led to the presence of A. salmonicida in the blood, but not at all in the kidney or spleen. Generally, A. salmonicida remained for up to 24 h at the sites of administration. The most effective entry site of A. salmonicida, leading to mortalities, was through the gill and anus. Fewer deaths resulted from challenge via the lateral line, flank and ventral surface.