The sample of 1129 respondents 18—30 years old (573 women and 556 men) were anonymously asked about their experiences with the sibling incest. In the sample of 794 men and women with a sibling in 6.5 % this type of incestuos experience was referred to. The most common victim was a younger sister, the most common perpetrator was an older brother. The average age of a victim in the beginning of these activities was 10.6 years, the average age difference between a victim and a perpetrator was 4,4 years. Most cases lasted about six months and common were also one time abuses. The most common incestuos activities were touching and mutual masturbation. Most of victims (89 %) felt negative consequences of these experiences, mostly somatic problems, depression, nightmares and anxiety, in most cases only transient ones. 93 % of victims did not announce this experience to anybody, only one čase was investigated and tried. About one fifth of the victims were beside the sibling incest abused also by another offender, mostly unknown, but also frequently by father. Victims and perpetrators of a sibling's incest were more often from the incomplete families, grown up with only one of parents or without own parents at all.

        Key words: sibling incest, forms, consequences