Prior to 1986 only two cases of atypical furunculosis were reported in the Maritimes. One of these involved Atlantic salmon (Salmo salar) in a Nova Scotia hatchery in 1974, the other case involved cod( Gadus morhua )held at the Halifax Laboratory in 1980. In the fall of 1986 and 1987 an atypical strain of A. salmonicida was isolated from Atlantic salmon mortalities in a New Brunswick hatchery. In 1987 a similar strain was also isolated from returning adult salmon from the Medway River in Nova Scotia. The third case involved a 2 year old Atlantic salmon held in brackish water at the St. Andrews Biological Station, N.B. Representative isolates from the three cases were biochemically characterized.