Abstract: The social systems of ants are far more variable than has traditionally been believed. In addition to variation in queennumber and queen mating frequency, recent research has documented such bizarre phenomena as the parthenogeneticproduction of females from unfertilized eggs or genetic caste determination. All these affect the genetic structure of antsocieties, and it appears that in a large percentage of species colonies do not consist of a single, singly mated motherand her sterile worker offspring. Though it has long been known that kin selection for reproductive altruism can workwell without a relatedness value between workers of 0.75, the recent upsurge of discussions about the role of relatedness in kin selection theory may have confused both myrmecologists and non-specialists. The aim of this review isto give an overview of the large range of ant reproductive systems and to correct some misconceptions about the role ofthe magic value 0.75 in kin selection theory.