A semiquantitative mean-field model for the thermally induced (heating-induced) polymer coil-to-globule transition (HCGT) is developed with no adjustable parameters. The transition temperature Theta is given for a long chain by the equation Theta = 2T*(p)[1 -(rho) over tilde (B)(Theta)], where T*(p) is the characteristic temperature of the polymer and (rho) over tilde (B)(Theta) is the bulk solvent density at the transition temperature. The variables (rho) over tilde (B) and T*(p) are obtained by invoking the Sanchez-Lacombe (S-L) equation of state. Calculated HCGT temperatures show good agreement with experimental lower critical solution temperatures (LCSTs). The predicted globular state is characterized by the dominance of attractive polymer self-interactions over excluded volume interactions. There is a critical value of the ratio of polymer to solvent S-L characteristic temperature below which no HCGT transition is predicted for an infinite chain. This model can be easily generalized to treat cross-linked gels and their contraction-expansion characteristics.