An extensive series of homopolymers and copolymers has been investigated to test earlier indications of a possible link between resistance to slow crack growth and creep of macroscopic oriented samples. It was found that in the majority of cases a good correlation exists between a single creep parameter and slow crack growth. The existence of such a correlation supports the model presented, in which crack growth is primarily controlled by the creep of fibrils spanning the craze zone. The limit of improvement achievable by increasing molecular weight and the greater effectiveness of short-chain branching to improve fibril creep have been highlighted.