One of the factors limiting the size of membranes in computer simulations is the large number of solvent molecules which fill the simulation cell. We have recently developed a novel computer model of bilayer membranes in which the membranes are simulated without the embedding solvent as if they were in vacuum. Using this new model we have been able to investigate the behavior of large membranes containing 1000 lipids. In the talk I will present the results of computer simulations demonstrating the efficiency of the model and its ability to mimic the physical behavior of bilayer membranes. I will explain some of the numerical results using theoretical arguments.