By any standard, there is a serious problem of crime on the public transport system in El Salvador. Guided by crime opportunity theory, this study undertook a rapid assessment of the problem consisting of a systematic observation of public transport in El Salvador and focus group discussions with passengers, bus operators, police and bus company owners/managers. The purposes were (1) to describe the main forms of crime and disorder afflicting the system, (2) to identify features of the system that contribute to the high levels of crime and disorder, and (3) to identify preventive measures, consistent with international experience. A program of situational crime prevention measures was identified which consisted of two main kinds: (1) measures relating to the operations of the bus system as a whole, intended to help to create a more orderly and secure transport environment and, (2) more specific measures designed to reduce opportunities for crimes occurring on buses or at bus stops, such as homicides, robberies, and sexual assaults on women. Future research and implementation of the preventive measures are discussed.