The results of a multicentre inquiry started in 1988 in reference centres of sudden infant death are presented. This study concerns the sudden and unexplained mortality of infants under 1 year of age who were treated with atropinics for an alleged risk of sudden death. The 7,851 infants involved were divided into 2,605 siblings, 1,067 premature babies and 4,179 infants who experienced malaises. Only one of the 2,034 infants treated with atropinics (385 siblings, 435 prematures, 1,214 with malaise) died, as opposed to 27 deaths among the 5,817 infants who where not treated (10 deaths among 2,220 siblings, 6 among 632 premature and 11 among 2,965 infants with malaise); P = 0.005. These results are encouraging, but they suffer from the limitations and biases inherent in all large inquiries. They certainly do not allow us to conclude without reservation that vagal hyperreflectivity is the mechanism responsible for sudden infant death and that atropinics must be systematically given to all infants at risk. Wide and randomized prospective studies are highly desirable in this particular field.