In Oregon, "Incompetent to Stand Trial (1ST) Patients" were observed to be increasing in number, remaining in the hospital longer, and costing more to treat. A study was designed to investigate variables that could be used to predict their length of stay at Oregon State Hospital. Data for thirteen independent variables (gender, age, having an Axis I psychosis level diagnosis, having an Axis I substance-related diagnosis, having an Axis II personality disorder diagnosis, evidence of involuntary medications, being on atypical medications at discharge, number of seclusion and restraint events, number of felony charges, number of misdemeanor charges, and number of inter-ward transfers) and one dependent variable (length of stay) were analyzed for 198 1ST patients discharged from Oregon State Hospital between January, 1999 and December, 2001. Bivariate correlations for all variables, and length of stay (LOS) means for all levels of each variable were examined and discussed. A standard multiple regression analysis was performed. The regression model accounted for 36.5% (32.7% adjusted) of the variability in (log) LOS. R for regression was found to be significantly different from zero. Five variables were found to be significant contributors to explaining the variability in (log) LOS: (square root) number of inter-ward transfers (16%), gender (5.8%), evidence of involuntary medications (5.2%), (square root) number of felony charges (2.8%), and (square root) number of seclusion and restraint events (1.6%). Despite accounting for more variability in LOS than several previous studies with psychiatric patients, 67.3% of the variability was unaccounted for by the regression model. Unstandardized regression coefficients for untransformed variables were interpreted, revealing that gender, number of inter-ward transfers, and evidence of involuntary medications significantly predicted the largest increases in LOS. Recommendations were made for further research related to LOS of 1ST patients. / Graduation date: 2003