Objective-The present study deals with a case study to understand the effect of formulation variables of microspheres of a model drug, levodopa (LD). Methods-A three-factor, three-level design of experiment (DOE) with response surface methodology (RSM) was run to evaluate the main and interaction effect of several independent formulation variables that included ratio of drug: polymer (X1), ratio of HPMC:carbopol 934p (X2) and agitation speed (X3) in LD microspheres. The dependent variables included swelling index (Y1), drug content (Y2), time of drug release (Y3), size (Y4) and percentage bioadhesion (Y5). A desirability function was used to minimize lag time and to maximize the other dependent variables. A mathematical relationship, for each of the above responses was obtained to explain the effect of all factors and their colinearities on formulation of microspheres. Results- The optimized microspheres were predicted to yield Y1, Y2, Y3, Y4 and Y5 values of 9.41, 99.58%, 6.5hrs, 23μm, 77% bioadhesion respectively, when X1, X2, and X3 values were1:2.81, 1:1.79 and 2200 rpm, respectively. A new batch was prepared with these levels of the independent variables to yield Y1-Y5 values that were remarkably close to the predicted values. Conclusion-This investigation demonstrated the potential of QBD in understanding the effect of the formulation variables on the quality of levodopa microsphere formulations.