From 1975 to 1989 multiple birth rate in The Netherlands increased with almost 40%. Only a quarter of the increase can be related to births after in vitro fertilization. Evidence is presented that ovulation induction as an independent therapy or in combination with other forms of assisted reproduction is highly responsible for the rising number of multiplets. As a consequence, a heavy burden is placed on the units for specialized neonatological care as well as on the obstetrical wards in the tertiary centres for neonatology. Doctors should become aware of the facts and should inform the public properly about the risks of multiple pregnancy. An international approach is needed to get insight in the problems and to develop effective policies for the future.