Recognition of prodromal symptoms of schizophrenia offers the potential of early intervention to avert relapse and re-hospitalization (Carpenter & Heinrichs, 1983). The present study investigated how a strategy to detect prodromal signs might be effectively applied in the clinical setting. A standard monitoring system was developed involving completion of a new early signs scale (ESS) measuring changes in key symptoms phenomenologically (self-report) and behaviourally (observer report). The ESS was subject to rigorous psychometric evaluation and tested in a prospective pilot investigation. The ESS reliably identified early signs and predicted relapse with an overall accuracy of 79%. Several different patterns of relapse were identified. Observer reports compensated for loss of insight in some patients. In two cases where early signs indices were detected, prompt increases in medication appeared to arrest relapse and avert readmission. The ESS offers itself as a reliable, valid and administratively feasible measure and demonstrates considerable potential as a cost-effective procedure for secondary prevention.