At present, the most popular protein crystallization method is vapor equilibration via the hanging drop method. This method, however, offers little control over the rate of equilibration between the growth solution and the reservoir. A device has been developed by the Center for Macromolecular Crystallography at the University of Alabama at Birmingham that offers precise control of vapor equilibration in the hanging drop method. We report herein qualitative crystallization data for selected proteins utilizing this device. These studies demonstrate that a slower controlled evaporation rate of protein growth solution generally resulted in smaller populations of larger protein crystals.