A dynamic mathematical model has been developed for multiple effect evaporator system. The application of the model has been demonstrated by using it to simulate the performance of evaporators described earlier by HOLLAND [9] and AGARWAL [1]. A good agreement, up to 98% accuracy, has been observed. The paper also discusses the effects of each operating variable on the total performance of the evaporator system. A sensitivity analysis has been conducted, which suggests that feed flow rate is the variable most vulnerable to cause deviations in other variables and affects the evaporator performance most significantly. The feed temperature is the least sensitive variable. The transient behaviour of the evaporator system has been resolved into a first order control dynamics equation and different control parameters such as K-p (gain factor), and tau (time constant) have been calculated. The simulations indicate that for caustic soda solution maximum values of K-p and tau are 1.3 and 34 respectively far the feed rate, and minimum values are 1.0, and 21 respectively for the feed temperature. For sugar solutions the corresponding values are 1.6 and 32 for feed flow rate and 1.2 and 20 for feed temperature. This study, we hope, may be useful in analysing actual performance of evaporators and designing control systems.