Objectives: The aim of this study was to investigate disclosure rates and disclosure patterns and to examine predictors of non-disclosure in a sample of male and female adolescents with self-reported experiences of sexual abuse. Method: A sample of 4,339 high school seniors (2,324 girls, 2,015 boys) was examined with a questionnaire concerning sexual experiences in this study with a focus on disclosure of sexual abuse (non-contact, contact or penetrating abuse, and including peer abuse). Results: Of the sample, 1,505 girls (65%) and 457 boys (23%) reported experience of sexual abuse. The disclosure rate was 81% (girls) and 69% (boys). Girls and boys disclosed most often to a friend of their own age. Few had disclosed to professionals. Even fewer said that the incident had been reported to the authorities. Logistic regression showed that it was less likely for girls to disclose if they had experienced contact sexual abuse with or without penetration, abuse by a family member, only a single abuse occasion or if they had perceived their parents as non-caring. Boys were less likely to disclose if they studied a vocational program, lived with both parents or had perceived their parents as either caring and overprotective or non-caring and not overprotective. Conclusions: Disclosing sexual abuse is a complex process. Much is hidden from the adult society, especially from professionals and the legal system. Since peers are the most common receivers of abuse information, programs for supporting peers ought to be developed. Differences in disclosure patterns for girls and boys indicate that a gender perspective is helpful when developing guidelines for professionals. Practice implications: Professionals, especially in the school system, need to be more aware of the finding that few sexually abused children seek help from professionals or other adults and that support offers should be directly addressed not only to the vulnerable young persons themselves but also to peers who wish to help a friend. (Contains 6 tables.)