The report provides a count of arrestees held on felony charges in six detention facilities in New Mexico on June 30, 2003 and estimates the annual cost of housing four categories of felony arrestees throughout the State: (1) probation and parole violators; (2) convicted felons sentenced to County facilities; (3) unsentenced probation and parole violators; and (4) arrestees sentenced to prison and awaiting transport to a State facility. Data were collected mainly from files maintained at six detention centers in New Mexico; detention facilities were selected on the basis of size, geographic location, and budgetary resources. Only 33.2 percent of arrestees fell into one of the four analyzed categories for which costs were calculated. Results indicated that 2,537 felony arrestees were held for 1 of the 4 categories. The cost per day for New Mexico detention centers ranged from $21 to $147. The State average cost per day was $55.49. Future research should further refine the felony categories used to calculate the cost estimates. Tables