ADDRESSED TO AN AUDIENCE OF LAW STUDENTS, THIS ARTICLE EXAMINES IN DETAIL THE VARIOUS TYPES OF HYMEN CONFORMATION OBSERVABLE IN WOMEN IN CONNECTION WITH PHYSICAL EXAMINTION FOR ESTABLISHING ADMISSIBLE EVIDENCE OF VICTIMS OF RAPE OR SEXUAL ASSAULT TO PROVE WHETHER ACTUAL PENETRATION HAS OCCURRED. TOTALLY RELIABLE, WORLDWIDE MEDICAL EVIDENCE EXISTS FOR CASES IN WHICH THE PARTICULAR CONFORMATION OF A WOMAN'S HYMEN SHOWS AN ELASTIC, EXPANDABLE OPENING WHERE NONE IS SUPPOSED TO BE, WHICH IS NOT AFFECTED BY MARITAL INTERCOURSE AND LASTS UNTIL THE BIRTH OF THE WOMAN'S FIRST BABY, WHICH COULD THUS BE TECHNICALLY DEFINED AS A 'VIRGIN BIRTH.' FORENSIC PHYSICIANS SHOULD BE AWARE THAT SUCH CASES ARE BY NO MEANS AS RARE AS THEY ARE GENERALLY ASSUMED TO BE AND REPRESENT ONE OF THE PITFALLS IN SECURING POSITIVE EVIDENCE OF A SERIOUS CRIME, SUCH AS RAPE, BECAUSE IT CANNOT BE OBTAINED BY THE MERE EXAMINATION OF THE STATE OF THE ALLEGED VICTIM'S HYMEN. ILLUSTRATIONS ARE PROVIDED. A BIBLIOGRAPHY IS APPENDED. --IN SPANISH. (LGR)