Filipin Complex is a mixture of four components: Filipin I, Filipin II, Filipin III, and Filipin IV. These compounds are 28-membered ring polyene macrolide antifungal antibiotics. Filipin complex has been found to alter cell membrane structure by interacting with the membrane sterols ergosterol and cholesterol. As such, filipin complex has become a useful tool for diagnosis of Niemann-Pick type C disease, and for detection and quantification of cholesterol in cell membranes. Filipin complex continues to find use as a marker for cholesterol trafficking in subcellular membranes.