To survey the level of disclosure of conception method within families of children conceived by conventional in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) and to examine the factors that might influence parental attitudes and plans for disclosure. In-depth questionnaire. Participants recruited through fertility clinics in the United Kingdom. Parents of children aged 5 to 6 years conceived by IVF/ICSI (n = 181; 51% survey response rate). Mothers and fathers of IVF/ICSI-conceived children were sent questionnaires to complete and return in a postage-paid envelope. Responses to the questionnaire. Most parents had told somebody about their child's method of conception, mostly close friends and family. Fewer (26% of mothers, 17% of fathers) had already discussed the child's mode of conception with their child. Fifty-eight percent of mothers and 57% of fathers intended to tell their child at some point. Sixteen percent of mothers and 21% of fathers were undecided. Four percent of fathers never wanted to discuss the subject with their child. Children were more likely to be told if conception was ICSI, rather than conventional IVF, and if an only child. Twenty-nine percent of undecided fathers and 36% of undecided mothers stated that they would tell their child if appropriate, child-friendly explanatory literature were available. The majority of parents wish to tell their child about their conception by IVF/ICSI at some point but are unsure as to the most appropriate timing and method of disclosure. Fertility clinics might have a role to play in providing the necessary support. Child-friendly literature might be helpful.