The research site was Orange County, Fla., in which Orlando, one of the largest urban centers in the State, is located. Orange County maintains comprehensive and reliable jail data that are sufficiently detailed to allow disaggregation of the daily number of persons confined in the county by pretrial and sentenced defendant classifications. The data for this study encompassed a 184-day period, from July 1, 1991, to December 31, 1991. The measure of criminal activity consisted of seven reported index crimes: willful homicide, forcible rape, robbery, aggravated assault, burglary, larceny-theft, and motor vehicle theft. The study used frequency of arrests made by police as the measure of arrest certainty. Pretrial incarceration was measured as the daily number of pretrial defendants incarcerated in jail in Orange County. Findings show a lagged negative effect of frequency of arrest on reported crime. As the number of arrests made by police increased, the number of index crimes reported to authorities decreased substantially the following day. Additionally, the analysis revealed a significant positive contemporaneous relationship between criminal activity and arrest levels. No feedback effects among the three variables were noted. Overall, the findings add empirical support to the thesis that the instantaneous and lagged relationship between crime and clearances are of opposite sign. That is, criminal activity increases arrest levels instantaneously, or at least relatively so, while the negative effect of arrest levels on crime levels occurs more gradually. 4 tables, 5 figures, and 67 references