The selective cyclooxygenase-2 inhibitory drug celecoxib is provided in amorphous form. Also provided is a celecoxib drug substance wherein the celecoxib is present, in at least a detectable amount, as amorphous celecoxib. Also provided is a celecoxib-crystallization inhibitor composite comprising particles of amorphous celecoxib or a celecoxib drug substance of the invention in intimate association with one or more crystallization inhibitors, for example polymers. Also provided is a pharmaceutical composition comprising such a celecoxib-crystallization inhibitor composite and one or more excipients. Also provided are processes for preparing amorphous celecoxib, a celecoxib drug substance of the invention, a celecoxib-crystallization inhibitor composite of the invention, and a pharmaceutical composition of the invention. Also provided is a method of treating a medical condition or disorder in a subject where treatment with a cyclooxygenase-2 inhibitor is indicated, comprising administering, for example orally, a composition of the invention in a therapeutically effective amount.