We have used powder X-ray diffraction, diffuse reflectance Fourier-transform infrared, Si-29 MAS NMR, N-2 adsorption, and transmission electron microscopy to examine the role of the concentration of silica, the surfactant, and the reaction time in the synthesis of high-quality silica mesoporous molecular sieve MCM-48, The XRD patterns of the products are consistent with the hexagonal --> cubic --> lamellar phase transformation.