Although precise laboratory methods for measuring psychopathology are not available, interviewer-rated instruments developed to assess symptomatology can be used to monitor schizophrenic patients undergoing rehabilitation. By regularly assessing patients, rehabilitation staff can improve the effectiveness of their interventions. Patients can be screened for high levels of symptomatology which might preclude assignment to rehabilitation programs with high levels of social stimulation. Monitoring the prodromal symptoms of relapse can sometimes prevent florid relapses and sustain a rehabilitative trajectory. Standardized instruments for measuring positive symptoms (e.g., hallucinations, delusions, and conceptual disorganization) and negative symptoms (e.g., affective blunting, amotivation, and asociality) are available. Monitoring target symptoms may be particularly cost effective in the rehabilitation milieu. Use of suggested operational criteria for defining clinical states such as relapse would improve outcome studies on rehabilitation interventions.