The camelids - camels, llamas and their relatives - are unique in producing antibodies that have no light chain. These single polypeptide chain antibodies bind to antigens as strongly as conventional, multi-chain antibodies, but have lower molecular weights, are easier to engineer and produce, and more stable. They are attracting a lot of interest as potential therapeutics and diagnostics. For therapeutics they can be engineered easily into small proteins that have all the potency of a conventional antibody, but with enhanced ability to penetrate the intercellular space, and so get at cellular targets. Camelid antibodies may also be better suited to penetrating the blood-brain barrier, and BBB-penetrating camelid antibodies have been developed suggesting a potential to target neurodegenerative disease. Their greater stability suggests that they would be more easily delivered orally or nasally rather than by injection. Some have speculated that their greater stability and (potential) low production costs mean they could be used outside high-tech, high-cost medicines in such applications as topical anti-bacterial agents or even in shampoo. For diagnostics and sensor uses their greater stability to denaturants and heat means that they can be used on sensors and point-of-care devices more readily. This talk will summarise the biology of these valuable biomedical tools, review the work being done at Cambridge on using them, and discuss how near we are to applying camelid antibodies as therapeutics to age-related disease.