This paper describes and compares the thermal schemes, thermal efficiency and thermal performance ratios of three different antiscalants (scale inhibitors) of 7.2 MIGPD Multi Stage Flash (MSF) distillers which have operated satisfactorily for an extremely long period. The evaluation tests conducted on the Multi Stage Flash (MSF) distillers revealed that all the examined antiscalants were successful in inhibiting alkaline scale formation and improving plant performance at top brine temperature ranging between 105 degrees C and 110 degrees C with respective dosing rates of 1.5 and 3.0 ppm. (C) 2009 Elsevier B.V. All rights reserved.