TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: Continuous reaction in a reactor with a solid catalyst bed, with reaction mixture flowing vertically downwards through reaction zones containing finely-divided (I) dispersed in a continuous alcoholic phase. Water is removed in stage (2), preferably together with at least some alcohol, preferably by selective separation using a membrane, or water is removed along with some or all of the alcohol by evaporation. More alcohol is added before stage (3), and stage (3) (or preferably the sequence of stages 2 and 3) may be carried out more than once. Alcohol is added to (II) in stage (1) in a mol ratio of 5-40, preferably 10-20; preferred alcohols are 1-5C mono- or poly-hydric alcohols. Preferred catalyst resins are strongly acid, polymeric, macroporous resins with free sulfonic acid groups. Preferred (II) are vegetable and/or animal fats and/or oils. Catalyst loadings in stage (1) and/or (3) are 0.1-4 (preferably 0.2-1.6) kg/kg/h for starting materials (II) with an acid number of 40 or less, or 0.3-10 (preferably 0.5-3) kg/kg/h for materials (II) with an acid number of more than 40. EXAMPLE - A mixture of rapeseed oil, oleic acid and linoleic acid with a free fatty acid content of 15.4 wt.% (acid number = 31 mg KOH/g) was passed at 740 g/h, together with methanol at 242 g/h, at 83 degrees C and 4 bar through a solid bed comprising 650 ml Amberlyst BD20 (RTM: acid ion exchange resin; 121 g dry catalyst material), with a residence time of 15 minutes. The catalyst showed a particle diameter of 0.8 mm and was immobilised in a solid bed reactor with a bed length of 2.08 m and a diameter of 20 mm. The reaction product showed a water content of 0.23 wt.% and an acid content of 0.48 wt.%, corresponding to a fatty acid conversion of 97%. The water content was then reduced to 0.04 wt.% by vacuum distillation (rotary evaporator). The residue (1098 g/h) plus methanol (290 g/h) was passed downwards through a vertical bed of the same catalyst under the same conditions as above, but with a residence time of 10 minutes; the empty-tube velocity of the reaction mixture was 1.39 mm/s and the mixture was fed in through a pipe with a circular opening of diameter 0.5 mm at its narrowest cross-section. In this further reaction, a continuous methanol phase containing dispersed oil droplets formed at the top of the reactor, with a sink rate of ca. 28 mm/s for droplets with an average diameter of 2 mm (much higher than the empty-tube velocity). After removal of methanol, the product showed an acid content of 0.07 (0.19) wt.%, i.e. a conversion of 87.8 (64.2) % based on free fatty acid entering this stage. Overall fatty acid conversion (two stages) was 99.6 (98.9) %. Values in brackets were obtained with an upward-flowing reaction mixture in the second-stage conversion.