Before a drug in tablet form can begin to work pharmacologically on a patient, it must first dissolve in the patient’s stomach before absorption into the bloodstream; this obvious first step can prove challenging to drug development. Dissolution apparatus is therefore necessary to provide information on the in vitro release of drugs in order to predict their in vivo behavior. There are seven USP-defined types of dissolution apparatus: baskets, paddles, reciprocating cylinders, flow through cells, paddle over disk types, cylinders, and reciprocating holders. Although USP 2 paddles are most widely used, most dissolution apparatus incorporate any number of each type (often all of them) . Dissolution apparatus – especially of the popular paddle variety – can suffer from hydrodynamic disturbances that can muddle test results; therefore, the customer should seek features that limit these disturbances, such as the motorized insertion and removal of the sampling cannula. While all available dissolution apparatus adhere to U.S. Pharmacopeia standards, only some adhere to U.S., European, and Japanese standards.