Both glucosamine sulfate and glucosamine hydrochloride (HCL) are forms of glucosamine. Glucosamine makes up 63 percent of glucosamine sulfate and 83 percent of glucosamine HCL. Most human studies have used glucosamine sulfate. This is because the company that paid for the research developed this form. Glucosamine HCL has not been evaluated as extensively, but clinical experience from a variety of health practitioners indicates that glucosamine HCL works just as well. Many health practitioners recommend trying one, and if that does not work, trying the other. ^AIMFrame Essentials™ gives you both of these at once.