Aluminium-containing mesoporous molecular sieves (Al-MCM-41) with different Al contents (Si/Al = 86.3, 43.9, 23.3, and 14.3) have been prepared using cetyltrimethylammonium bromide as an organic surfactant and characterized by XRD, MAS NMR, and Nz sorption studies. Al-27 NMR studies reveal that the Al is present in Td coordination in the samples. The samples were loaded with Pt and used in the hydroisomerization of n-hexane. The reactions were carried out at atmospheric pressure in the temperature range of 300-400 degrees C. The optimum Pt content for the reaction was found to be around 0.3%. High selectivities for isomerization were observed.