This article contains a detailed analysis of the melting process of poly(butylene terephthalate) performed by means of temperature-modulated differential scanning calorimetry at various temperature-modulation frequencies. The modulation period largely affects the apparent reversing specific heat capacity (c(p)), but not the total C-p. An interpretation based on the analysis of the latent heat involved in the process is proposed. In addition, a detailed examination of the modulated heat-flow-rate curves is presented. The finding is that the melting process of poly(butylene terephthalate) is the sum of simultaneous events of the melting of small and defective crystals and their immediate recrystallization into more stable structures. (C) 2004 Wiley Periodicals, Inc.