The project evolved from a discussion between academic staff at Loughborough University of Technology and staff from the British Petroleum Co. Ltd. A study was required of the dynamic characteristics of a particular 44-plate crude oil distillation unit at BP Refinery (Llandarcy) Ltd. A programme of experiments was conducted on the industrial unit. Step perturbations in the overhead reflux and sidestream off takes were found to give oscillatory response curves decaying over a two-hour period. A qualitative explanation for these results is given.