In situ formation of the micro- and mesoporous structures MFI and MCM-41 was obtained using a two-template syntheses gel system [C 6 H 1 3 (CH 3 ) 3 NBr and C 1 4 H 2 9 (CH 3 ) 3 NBr]. The mixed phases were obtained by optimizing template concentrations and reaction temperatures. Constant temperature syntheses as well as sequential high/low or low/high temperature strategies were performed successfully. It was found that the relative amounts of the two structures MFI and MCM-41 in the final products can be controlled by varying the ratio of the templates and by tuning the synthesis temperature. Characterization results indicate that phases of varying complexity were obtained.