This paper is concerning the Analysis of multi stage flash (MSF) desalination plant performance, the analysis covers the operation period (January 1999-December 2000). This unit with a nominal capacity of 100 m(3)/hr, consists of 12 stages (9 for heat recovery and 3 for heat rejection), and has been in operation since 1982. The unit has been evaluated for its performance ratio, thermal efficiency, capacity factor, availability factor, plant capacity factor; other parameters related to performance have been examined too. It is found that the unit is operating below their designed capacity with annual average plant factor ranging from 0.69 to 0.76 over the years 1999 and 2000. The thermal efficiency and performance ratio are found to be lower than designed values. Low performance ratios are the result of high steam consumption and low production rates of distillate water. Some operating problems were experienced. In this study, the important design factors and operating conditions are reviewed and the plant operating data were used to evaluate the unit performance. The water production cost is estimated and it is found to be 0.942 LD/M-3 (0.628 $/M-3). In spite of 18 years of operation and the frequent technical problems, the unit performance is quite good which has been reflected on the water production cost. Comments, conclusions and recommendations derived from this evaluation are presented.