In partnership with the Adult Probation Department in Pima County, Arizona, and as part of broader research funded by the Safety and Justice Challenge to examine the impact on jail use of providing housing supports for people on probation in Pima County, the Urban Institute analyzed trends in jail incarceration for people with probation violations using datasets for overall jail bookings in the county from 2015 to 2020 and petitions-to-revoke for people on probation from 2016 to 2020. This case study summarizes our findings on patterns in overall jail bookings and petitions-to-revoke and, for the probation population in jail, analyzes average lengths of stay and patterns by race and ethnicity and sex.