Tancreas disease' is a syndrome of unknown aetiology affecting farmed Atlantic salmon, Salmo salar L., particularly in Scottish sea-caged sites {Munro, Ellis, McVicar, McLay & Needham 1984). The condition is reported to affect fish in their first year in salt water and to cause low mortality, with recovery several weeks or months later. Described lesions include loss of pancreatic exocrine tissue and fibrosis. The present report extends the pathological observations to describe briefly a severe degenerative myopathy involving the heart as well as red skeletal muscle; these lesions developed concurrently with the pancreatic condition, in affected fish.Fish were sampled from two sea-cage sites over a 3-month period. Samples included both clinically sick and healthy fish. Affected fish were dark, thin, anorexic and lethargic; they congregated in the corners of cages and frequently failed to maintain a horizontal position, falling down to rest on the net sides. Many such fish had eroded and ulcerated fins and skin. When netted out into containers for closer examination, they frequently died, and entered rigor more quickly than clinically healthy ones.Tissues were fixed in 10% buffered formalin for routine processing to haematoxylin and eosin (H&E) stained paraffin wax sections. Tissues sampled included heart, skeletal muscle, skin, brain, kidney, pancreas and pyloric caeca, oesophagus, stomach, liver, spleen and gills.Major lesions were consistently present in the heart, skeletal muscle and pancreas of sick fish at both sites. Changes in the heart were characterized by coagulative necrosis of ventricular myocardium, affecting both spongy and compact layers (Fig. 1). There was loss of striation, and increased eosinophilia with granular and vacuolar change. Atrial myocardium was also affected, although less commonly. Mural thrombi were sometimes present on endocardium, especially in severely affected hearts. Some fibres contained macrophages and a proliferation of satellite-type ,sub-endocardial cells, so that in some areas or entire hearts, the picture was dominated by an increased cellularity suggesting repair. Similar changes were found in skeletal muscle mainly in the red fibres along the lateral line, although occasional fibres in the rest of the body muscle were also affected. A few fish had similar degeneration of oesophageal muscle. Pancreatic tissue was markedly