From bacteria to man, ABC transporters comprise the largest family of membrane proteins. They participate in most physiological processes and are directly linked to human disease, tumor resistance to multiple chemotherapeutics, bacterial multidrug resistance, and bacterial virulence and pathogenesis. Recent results demonstrate that different ABC transporters are of different architectures and operate by different mechanisms. Here I will discuss how this structural and mechanistic diversity is linked to the diversity of physiological roles of ABC transporters, and how such molecular fine-tuning provides solutions for a variety of metabolic needs.