This paper describes results from an experimental investigation into the scale-up of oscillatory flow mixing (OFM) in geometrically scaled baffled tubes ranging from 24 mm to 150 mm diameter and from 1 m to 4.5 m in length. Measured axial dispersion coefficients are reported together with case studies and an empirical correlation. An alternative multi-orifice reactor geometry with the potential for use in large-scale plant was also constructed and tested from which it was concluded that OFM is a technology which lends itself readily to scaling-up from laboratory to pilot plant scale, and to industrial scale. Experiments performed on small laboratory OFM apparatus containing less than one litre of fluid can with confidence be used to predict mixing behaviour in much larger plant containing hundreds of litres of fluid.