A severe, fatal, exudative peritonitis was investigated in a flock of 100 breeding fitchMustela putorius furo. The presence of enteric flora within the lesions and steel spicules within the stomach contents suggested that this disease may have been caused by steel fragments perforating the intestine. Scoring and pitting of a steel mincer plate used for food preparation consistent with the size and shape of the steel particles found in the stomach, further supported this hypothesis. There were no further cases when the feed source was changed.