Each year NSW Police receive reports of more than 7,000 sexual and indecent assault incidents. Only about one in ten of these incidents result in someone being found guilty in court. This paper analyses data from police and the criminal courts to ascertain the stages at which sexual offences lapse from the criminal justice system. Most sexual offences proceed no further than the investigation stage. Only 15 percent of sex incidents involving a child victim and 19 percent of incidents involving an adult victim result in the initiation of criminal proceedings against a suspect. Among the small proportion of cases that do reach court, the conviction rate is low, with less than 50 percent of defendants appearing for a sexual offence being found guilty. Criminal proceedings are less likely to be commenced in incidents where the victim is a young child, where the incident is reported more than ten years after it occurred, where the offender is a stranger and where there are no aggravating circumstances. These factors affect the quality and availability of evidence and suggest that the decision to prosecute is influenced mainly by the strength of the case and the prospect of success in court. It is suggested in this paper that every effort be made to strengthen cases at the investigation stage by the comprehensive gathering of evidence and the support of victims in order to improve the response of the criminal justice system to sexual assault.