The time course of crystallization of hard fat suppository bases has been studied by isothermal DSC, nuclear magnetic resonance spectroscopy, oscillation rheometry, and thermorheography.The crystallization of hard fats was found to be a biphasic process, where the content of partial glycerides and the extent of supercooling determine the formation of crystal nuclei while the final solidification level depends upon the crystallization temperature.The principles of different techniques and results are compared considering potential applications in process surveillance and quality control. The methods employed could also help to enhance pharmacopoeial specifications.