It is widely believed that people can remember the age at which they first had sexual intercourse. Questions about age at onset are routinely asked in population sexual behaviour surveys and in clinical history-taking. However, there are limited test–retest data, especially with regard to individual differences in unreliable recall. In this study, telephone interviews and follow-ups an average of 15 months later were conducted with 570 non-virgin subjects aged between 28 and 73 years. Test–retest correlations for recalled age at first intercourse were 0·85 for females and 0·91 for males. Consistency was slightly lower among older people and women with a history of sexual abuse. There were no significant associations between consistency of recall and measures of personality, educational background or history of alcohol dependence and depression.