Several intervening variables may inยฏuence motor evoked potentials (MEP) from transcranial magnetic stimulation (TMS). Among the most common are motor (e.g. executed or intended muscle contraction) and sensory factors. However, little is known about the effects of a well deยฎned stressor on MEPs and thus on central motor control. We studied 11 healthy right-handed volunteers ( ยฎve men and six women), aged 21ยฑ32 years (mean 25.2 years, SD 3.5). All subjects underwent a 20 min rest and a 20 min stress period (sequence-controlled, cross-over design). The stressor employed a competitive videogame. MEPs from the left abductor digiti minimi muscle were obtained immediately after rest and stress. We found that six (54.5 per cent) subjects presented a signiยฎcant increase (p 5 0.05) of MEP amplitudes from rest to stress, three (27.3 per cent; p 5 0.05) decreased, and two (18.2 per cent) did not change. F-and M-waves did not change signiยฎcantly. Psychological testing (state and trait anxiety inventory, STAI) revealed that individuals who presented an increase in MEP latency scored lower in state and trait anxiety than others, probably indicating a lower vulnerability to stress. We believe that the observed increase in MEP amplitudes, combined with a decrease in MEP latency, can be regarded as neurophysiological evidence of stress-induced facilitation related to higher excitability of the corticospinal system and/or presynaptic neurons.