This paper evaluates the effectiveness of the Program for Pollution Control Evaluationand Rating (PROPER) in Indonesia. PROPER, the first major public disclosure program in thedeveloping world, was launched in June 1995; though it collapsed in 1998 with the Asianfinancial crisis, it is currently being revived. There have been claims of success for thispioneering scheme, yet little formal analysis has been undertaken. We analyze changes inemissions concentrations (mg/L) using panel data techniques with plant-level data forparticipating firms and a control group. The results show that there was indeed a positiveresponse to PROPER, especially among firms with poor environmental compliance records. Theresponse was immediate, and firms pursued further emissions reductions in the following months.The total estimated reductions in biochemical oxygen demand (BOD) and chemical oxygendemand (COD) were approximately 32%.