In particular with the earlier representatives of modern antifungal inhibitors, the modes of actions were clarified long after the respective fungicides and antifungal agents had been introduced. The overall antifungal activity evaluated in biological screening tests is the most integral and almost perfect biological parameter of a newly synthesized compound. The ideal antifungal inhibitor should be highly enzyme specific, it should easily reach the target site, and it should react in a 1:1 inhibitor/enzyme ratio. The latter demand implies that enzymes present in low concentrations would require less quantities of inhibitors and, thus, would be superior targets. The actual number and nature of enzymes and receptors affected by existing site-specific antifungal agents is in surprising contrast to this assumption. All of the “established” inhibitors with proven records in fungal control have evolved from random screening programs and, thus, were selected and developed according to their biological performance rather than their respective target sites.