A discussion of flight experience obtained on a 250 lbf thrust monopropellant hydrazine thruster is presented. Consistent and highly predictable performance was achieved over the full range of operating conditions, and the catalyst bed resistance parameter was employed successfully in performance prediction. An unexpected decline in catalyst bed resistance, not observed in previous ground testing, caused initial concern over possible engine washout, although eventual stabilization occurred. Analysis of ground and flight data indicates incomplete simulation in ground testing, and suggests caution in the extrapolation of flight thruster life expectancy from ground test results.