Chicago's rapid rail transit system reports about 15,000 crimes yearly, and transit crime costs the city approximately $100 million annually. These costs include police surveillance, operational expenses for other labor-intensive deterrent systems, reduced ridership, lost revenue due to fare evasion, equipment down-time, repair and replacement of vandalized equipment, court processing fees, incarceration, hospitalization, and liability insurance. An analysis of on-site observations at subway stations and on-site interviews with transit police officers and Chicago Transit Authority booth agents indicates that high crime station sites offer perpetrators visual access to most areas surrounding the sites. High incident sites for crimes against persons attract large, congested crowds or people in isolation. Transit employees are often not able to pay attention to an incident, not able to respond to observed incidents, or not within visual access to an incident. High crime station sites always have more than one primary escape alternative and several secondary escape alternatives. Proposed guidelines to reduce the likelihood of transit station crime involve moderating crowd size, creating predictable crowd movement patterns, minimizing crowd congestion and isolated individuals, minimizing opportunities to observe prospective victims without being seen, and offering fewer exit and escape alternatives. Prototypical transit station designs incorporating these guidelines are presented. Appendixes contain additional information on the study methodology and results. 81 references, 59 figures.