The all-round effect of dissolved oxygen concentration, agitation speed, and temperature on the rosmarinic acid production by Lavandula vera MM cell suspension was studied in a 3-L laboratory bioreactor by means of the modified Simplex method. Polynomial regression models were elaborated for description of the process of rosmarinic acid production (Y) in the bioreactor as a consequence of the variation of the dissolved oxygen (X(1)) concentration between 10% and 50%; agitation (X(2)) between 100 and 400 rpm; and temperature (X(3)) between 22 and 30 degrees C. The optimization made it possible to establish the optimal conditions for the biosynthesis of rosmarinic acid by L. vera MM: dissolved oxygen (X(1)*), 50% of air saturation; agitation (X(2)*), 400 rpm; and temperature (X(3)*), 29.9 degrees C, where maximal yield (Y(max)) of 3489.4 mg/L of rosmarinic acid was achieved (2 times higher compared with the shake-flasks cultivation).