Transesterification between a liquid crystalline polyester and poly(butylene terephthalate) was followed quantitatively by analyzing C-13-NMR spectra of the 50:50 blend after heat treatment at 290 degrees C for varying lengths of time. Differential scanning analysis was employed to follow the interchange reactions. From analysis of triad sequences of the transesterified blends, it was clear that measurable exchange reactions occurred when the blend was kept at 290 degrees C for 20 min. The distribution of sequences tends to approach that of a statistical binary copolymer as the heat : treatment period is Increased. The results obtained from this investigation show that polyblends between an LC polyester and conventional polyesters must be handled carefully. Otherwise, ester interchange reactions are inevitable.