The synthesis of a novel, large-pore, high-silica molecular sieve, NCL-1, is described in detail. A comparison of the XRD powder patterns of NCL-1 and other known structures revealed that zeolite NCL-1 is a new phase. However, zeolite SSZ-31, a Chevron material, and NCL-1 have some common features and may belong to a common family. Adsorption measurements ( o-xylene = 7.4 and mesitylene = 4.8 wt% at P P o = 0.5 , T = 298 K) rank NCL-1 as a large-pore zeolite. The synthesis has been carried out using fumed silica, aluminum sulfate (optional), and hexamethylene bis(triethylammonium bromide) (R 2+) as an organic template under hydrothermal conditions in alkaline medium. The kinetics of crystallization has been studied using X-ray powder diffraction, scanning electron microscopy (SEM), and framework i.r. spectroscopy. The influence of various synthesis parameters such as the Si Al and Na + Si molar ratios, alkalinity ( OH − Si ), concentration of the organic template ( R 2+ Si ), the H 2O Si ratio, and the temperature on the crystallization time, phase purity, and yield of crystalline product has been investigated.