This study was a replication of a portion of the Kansas City Police Department's study entitled 'Response Time Analysis.' This study focused on citizen delays in reporting crimes to police in Jacksonville, Fla.; Peoria, Ill.; Rochester, N.Y.; and San Diego, Calif. The study is based on interviews with over 4,000 victims, witnesses, and bystanders in some 3,300 serious crimes (aggravated assault, auto theft, burglary, larceny, rape, and robbery). Findings confirm the conclusion of the Kansas City study that citizen-reporting time, and not police response time, most affects the possibility of on-scene arrest and that when citizens delay in reporting crimes, efforts to reduce police response times have no substantial effect on arrest rates. Citizen delay time is relevant to apprehension only when the citizen is involved as the crime is being committed. In such cases, speedy reporting to the police combined with fast police response time increases the likelihood of apprehending the offender at or near the crime scene. Causes for citizen delay in reporting crimes include ambiguity about whether or not a crime is actually being committed, first priority given to coping with problems the crime has created, conflict about whether or not to call the police, no phone readily available, did not know the police telephone number, and trouble communicating with a person taking the call. Approaches that can reduce the influence of these factors in delaying crime reporting to police are discussed. Tabular and graphic data are provided, along with a bibliography of about 110 listings.