Since 1980, there has been a worldwide dramatic increase in multiple births. This seems to be due to an increase in the age of reproduction, the use of ovulation induction, and the use of in vitro fertilization. Scarce data suggest that each of these causes is responsible for about one-third of the problem, although quintuplets and more are almost invariably due to ovulation induction. There has been little or no effort to issue guidelines or regulations with respect to ovulation induction, but there has been much advice as to how to control the problem in in vitro fertilization by limiting the number of embryos to be transferred. In sum, a good selection of high-quality embryos on day 3 would allow a high rate of pregnancy with the transfer of one or two blastocysts. Good results of cryopreservation must be part of an agreement in an in vitro fertilization program. If singleton live birthrates were considered to be the principal outcome of assisted reproductive technologies reported by centers and registry, twin and triplet rates should also be reported separately. And finally, if financial considerations would not limit the cost of reimbursement to in vitro fertilization procedures, the number of procedures could be increased with fewer embryos transferred.