Diphtheria seemed to have disappeared from Europe. Now it has returned to our doorstep, just a two-hour flight from Paris, in all the countries of the former Soviet Union on the one hand, and in Algeria on the other. In France, no cases of diphtheria have been reported since 1987. The last major French epidemic dates back to the 1940s, at the end of World War II, when tens of thousands of cases were recorded. The establishment of a "Study Group on C. diphtheriae Infections" therefore provides an opportunity to take stock: 1/ On diphtheria in France and worldwide, 2/ On other forms of infections associated with C. diphtheriae, 3/ On the progress made in the epidemiology of these infections, particularly through molecular biology. (R.A.).