A continuous reactor process was developed to produce lactulose from lactose. A system of two CSTRs in series with a tubular finishing reactor gave conversion to lactulose of about 76%. The reactors ran at 71-75-degrees-C with a volumetric hold-up in the CSTRs of 22.7 dm3 and in the tubular reactor of 2.6 dm3. Each CSTR had a nominal residence time of 44 min. The flow rate was 0.53 dm3 min-1.