AbstractThis paper discusses the applicability of three melting equations to the melting temperature and its pressure dependence in polymer crystals. The equations considered are the empirical Simon equation and two semiempirical equations, the Lindemann equation and the anharmonic potential barrier equation (APB equation). It was found that although the Simon equation fits melting curves of polymeric solids well, it is merely an interpolation and extrapolation formula. There appears to be no correspondence between theoretical and experimental values of the exponent in the Simon equation. With regard to the melting temperature at atmospheric pressure, the APB and Lindemann equations perform equally well. Using the value 3.5 for the universal Grüneisen constant, it is shown that T (Lindemann) = 1.07 T (APB). On the other hand, the different physical arguments behind the two approaches lead to a very different behavior at high pressures. For the predicated initial change of melting temperature with increasing pressure a ratio close to 5:1 is obtained between the APB and the Lindemann equation. For high‐density polyethylene the Lindemann equation yields a melting temperature of 470°K when θ3 = 112°K given by Wunderlich is substituted for the Debye temperature. The observed melting temperature 405°K Corresponds to a Debye temperature of 107°K. The increase of the melting temperature with pressure for high‐density polyethylene is predicted as 31°K/kbar by the Lindemann equation as compared with 23°K/kbar found by experiment.