To determine whether [(18)F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) could predict the pathological response in oesophageal cancer after only the first week of neoadjuvant chemoradiation. Thirty-two patients with localised oesophageal cancer had a pretreatment PET scan and a repeat after the first week of chemoradiation. The change in mean maximum standardised uptake value (SUV) and volume of metabolically active tissue (MTV) was compared with the tumour regression grade (TRG) in the final histology. Those who achieved a TRG of 1 and 2 were deemed responders and 3-5 nonresponders. In the responders (28%), the SUV fell from 12.6 (+/-6.3) to 8.1 (+/-2.9) after 1 week of chemoradiation (P=0.070). In nonresponders (72%), the results were 9.7 (+/-5.4) and 7.1 (+/-3.8), respectively (P=0.003). The MTV in responders fell from 36.6 (+/-22.7) to 22.3 (+/-10.4) cm(3) (P=0.180), while in nonresponders, this fell from 35.9 (+/-36.7) to 31.9 (+/-52.7) cm(3) (P=0.405). There were no significant differences between responders and nonresponders. The hypothesis that early repeat FDG-PET scanning may predict histomorphologic response was not proven. This may reflect an inflammatory effect of radiation that obscures tumour-specific metabolic changes at this time. This assessment may have limited application in predicting response to multimodal regimens for oesophageal cancer.