The theoretical basis for inflated tire calculations is explained, and models of the tire are developed that exhibit a high degree of accuracy. After establishing the fundamental equations common to the various models, the simplest case, a net of inextensible cords, is treated. The effects of cord extension and angular distributions different from the simple cosine law are then considered. It is shown that for each model it is convenient to proceed to a particular form of the fundamental formula in order to simplify the calculations and to clarify the influence of the various parameters. These models are of value for conventional tires; in the case of radial tires it is only possible to study the part of the carcass away from the belted zone.