The general approach to analysis of the kinetics of protein aggregation registered by the turbidimetric method has been elaborated. The terminal part of the kinetic curves is analyzed using a theoretical equation connecting the derivative of the apparent absorbance (A) with respect to time (dA/dt) and A (t is time). This analysis allows the limiting value of A at t→∞ (Alim) and the order of aggregation with respect to protein (n) to be calculated. Approach proposed was applied to analysis of thermal and acidification-induced aggregation of firefly luciferase. In both cases the Alim value is a linear function of the protein concentration. The terminal part of the kinetic curves of thermal aggregation follows the first-order kinetics (n