The effects of total haem pigment content of pork muscle on the potential for the formation of nitric oxide pigment during curing are reported. A linear relationship between the amount of endogenous pigment present and yield of nitric oxide pigment was found. Although the conversion to nitric oxide pigment was far from complete, the reducing capacity of muscle was more than adequate to convert all the haemoprotein present to nitric oxide pigment. The role of myoglobin and haemoglobin in these conversions is discussed.