“…We expect to find a much lower percentage of resident physicians in the active category, due to a high work load combining extensive training and patient treatment activities [Michie and Sandhu, 1994;Butterfield, 1998]. In Mexico, first year residents have little decision-making latitude; they basically carry out medical procedures ordered by more advanced residents and staff physicians.Studies of resident physicians have evaluated sleeping hours and their consequences in car accidents, resident physician's satisfaction [Perry and Osborne, 2003] and contrasting the quality of life between resident physicians and staff physicians, including depression, drug abuse, loneliness, marriage breakdown and cognitive damage [Sargent et al, 2004]. But there are no studies regarding resident physicians' stress using the demand-control model and HRV.…”