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seizure activity after high voltage head-only stunning includes a tonic and two clonic phases (Velarde et al., 2002). Anecdotal experience of the Dialrel WP2 members revealed that in examples of bad routine practise, between 4 and 20 percent of sheep may be ineffectively stunned because of wrong positioning of the electrodes. This is often due to inadequate restraint in relation to slaughter speed, too short application time of current and late sticking. In poultry two stunning methods are used in the context of reversible electrical stunning: head-only electrical stunning, where the current is applied only to the head via a pair of electrodes, and electrical water bath stunning where high frequency currents are used that do not induce cardiac arrest. For both methods the depth and duration of unconsciousness depends upon the amount and frequency of currents applied (EFSA, 2004, page 116 ff.). The frequencies used in modern electrical stunning systems of poultry ranges from 50 to 1500 Hertz. Waveforms of currents are pulsed direct currents (DC) and sine wave alternating currents (AC). As a consequence of the variations in waveform and frequency, measurement of current amperage has become sophisticated. Depth and duration of unconsciousness induced with all the waveform frequency combinations used in practice, have to be determined based on sound scientific studies with special regard to the variable conditions in practice (EFSA, 2004, page 120; Wenzlawowicz and Holleben, 2001; Gregory and Wotton, 1986). High frequency electrical stunning is important in poultry stunning, because it leads to a more even and less pronounced contraction in the muscles and thus helps to prevent blood blemished meat. Other possible carcass downgrading like broken bones and red wing tips are also reduced. The disadvantage of high frequency stunning is, that a shorter lasting stunning effect is produced, especially in the quickest recovering birds (Mouchoniere et al., 1999; Wilkins et al., 1998; Hillebrand et al., 1996) and extra care is needed in checking that birds remain insensible throughout the bleeding period (Gregory, 2007). Poultry, unlike red meat species, do not show grand mal epilepsy in the brain following electrical stunning. Nevertheless scientific literature suggests that the electrical stunninginduced release of monoamines and inhibitory amino acid neurotransmitters in the chicken brain may play a prominent role in the induction and maintenance of unconsciousness following electrical stunning (Raj, 2003). These mechanisms would also appear to be relevant to the manifestation of a profoundly suppressed EEG and abolition of SEPs following electrical stunning, which are suggested to be meaningful indicators of an effective electrical stun in chickens. Research to date indicates that electrical stunning indicative of unconsciousness in chickens should lead to a period of spike-and-wave epileptiform activity. This is followed by a period (of at least 30 seconds) of profoundly suppressed or quiescent EEG immediately thereafter, indicative of spreading depression or neuronal fatigue in the brain (Sch端tt-Abraham et al., 1983a). Return of eye reflexes and normal breathing are useful indicators of the early return of brain function after electrical stunning of poultry. Whereas a reaction to comb pinching or return of neck tension are not considered useful, as their return appears to be very late relative to other functions. During bleeding vocalisation and wing flapping must be absent as well as head raising, spontaneous blinking and directed eyeball movements (focused on stimuli from the environment) (Wenzlawowicz and Holleben, 2001; Sch端tt-Abraham, 1999). Head only electrical stunning is used commonly to stun poultry on the farm and as a back-up method. For head-only stunning the birds are restrained by hand, in a cone or shackles, between the legs or in a crush and the current is delivered by a pair of tongs or fixed