The green muscle disease (GMD), described for the first time in 1968, is a cause of significant losses in the production of turkey meat. Pathological changes of different intensity are found in smaller pectoral muscles on one or both sides of the sternal crest. GMD has been more frequently observed in Poland since 1991 in breeding turkeys of heavy and medium-heavy types assigned to slaughter after completing the reproductive period. The present study deals with the occurrence of this disease in the Warmia and Mazury District of Poland. Characteristic green foci located in small pectoral muscles were found in 4090 out of 26,169 slaughtered turkeys, i.e. in 15.63% of the carcasses investigated. It was established that 2430.5 kg of meat were confiscated what gave 0.59 kg of confiscated meat per head on the average.