Abstract: A gel fixative composition having increased, viscosity which fixes tissues as well as or better than standard liquid fixative solutions. The gel fixative compositions are less prone to leakage and are less likely to splash or spill from containers when they are mishandled. Because of their viscosity, they are less likely to penetrate surfaces and are more easily cleaned up if spilled. A method of making mixing biological fixative by mixing a solution of a biological fixative with a with a high-shear mixer at about 400 to 600 rpm; dispersing uniformly over time about 0.2 to about 2.0 weight percent of thickener while mixing for 2 to 10 minutes; increasing the mixing speed to about 1000 to 1500 rpm; and then, mixing for about 90 to 120 minutes so that a gel fixative composition is formed having a viscosity between about 1,000 cp and 200,000 cp.