The purpose of this study was to establish medico-legal guidelines based upon medical findings which support or refute allegations of sexual penetration, taking into account non-sexual explanations for positive physical findings. A review of the literature was undertaken to examine what has been determined about the range of usual findings which can be expected if the hymen has been penetrated. While a large body of literature is available on the topic, some findings are ambiguous, and further research is required to advance and clarify our knowledge base in these areas. In only a minority of non-acute cases can definitive statements be made as to whether an alleged molestation has occurred. A non-scarred hymen that will not admit a finger is 'intact'; a hymenal opening accommodating two fingers or a vaginal speculum, with evidence of a deficit or scarring at the lower pole, indicates past sexual or, possibly, non-sexual penetration. Other findings are not definitive and, at best, can estimate only relative probability of occurrence of penetration. Findings within the normal range should be presented as 'neither confirm nor deny abuse', not 'consistent with abuse'. Often, it is impossible to establish whether a hymen is 'intact' in regard to past sexual intercourse.