It has long been known th at stress during the slaughter period may result in the production of meat with major quality defects, particularly PSE and DFD meat. Recent studies using behavioural, physiological and/or genomic approaches fou nd that Jess extreme stress levels during slaughter may a iso influence technological and/or sensory quality of meat of pigs, cattle, sheep, and fowl and of fish flesh, sometimes explaining over 70% of inter-animal variability. Stress reactivity at slaughter varies between animais and may be predicted from reactions to stressful challenges during the rearing period. The stress reactivity of an animal depends partly on its earlier experiences and genetic background. In addition to slaughter-related animal welfare questions, today's challenge is to increase our understanding of the physiological and molecular mechanisms underlying the effects of stress on meat quality. The different species should be taken into account, as the causes of stress at slaughter and criteria for optimal meat quality are species-specific. In addition, the mechanisms underlying the effect of stress on meat and flesh quality differ at !east part! y between species.