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The research undertaken in this thesis includes microwave-assisted extraction (MAE), synthesis, and the investigation of the scale-up of the microwave-assisted processes with the numerical aid. / The main goal of this research is to study the various problems associated with the scale-up of the microwave-assisted extraction and synthesis processes. Laboratory studies were carried out to investigate the microwave-assisted extraction of known components from peppermint leaves and American ginseng. Various factors that influence the extraction processes were studied. Microwave-assisted extraction method was compared with conventional heating and room temperature extraction methods on the extraction of ginsenosides from American ginseng. Microwave-assisted extraction method was determined to have higher extraction rate than both room temperature extraction and reflux temperature extraction using hotplate heating indicating that there is acceleration factor in enhancing the extraction rate beyond the temperature influence. / In the study of synthesizing n-butyl paraben, microwave-assisted synthesis was observed to greatly increase the yield of n-butyl paraben in much shorter period of time compared to the classic synthesis method. A transition state theory was proposed to explain this rate enhancement. The study of the synthesis of parabens with different alcohol and the influencing factors on the synthesis of n-butyl paraben yield were also studied. / A visualization method was developed to determine the microwave distribution in a domestic microwave cavity. The method uses gypsum plate as carrier and cobalt chloride as indictor. A simulation program was developed using the finite difference time domain (FDTD) approach and written in C programming language. The program was proved to be very versatile in different type of cavity simulation. Not only cavities with different dimensions and geometrical designs can be simulated, multiple magnetrons and various ways of magnetron placement can also be integrated into the simulation program. The detailed power distribution can be visualized in a 3-D plot, and the power distribution in each layer can be analyzed using the simulation result. The power distribution information will be very useful and necessary before any real equipment development.