Immobilised enzyme-catalysed conversions frequently provide specific advantages of selectivity overchemical conversions and further, facilitate continuous operation through biocatalyst retention andreuse. This study focuses on the development and modelling of an enzyme-catalysed continuous immo-bilised enzyme biocatalytic membrane reactor (BMR). The conversion of the amidase-catalysed lactamideto lactic acid process was used as an industrially representative system with which to evaluate the processperformance of the BMR.The model was developed from unsteady state differential mass balances incorporating a second orderenzyme decay. This model was validated from empirically determined conversions in dual experimentsusing 80 and 40 mM amide substrate, 6.4 and 20.1 mg immobilised amidase and a flow rate of 0.0005 and0.0001 L/min respectively.Model predictions over a range of amidase amounts and stabilities, flow rates and initial amide con-centrations quantified the direction and extent of the influence of these parameters on the maximumconversions attainable, consequently identifying the critical parameter ranges defining optimal BMR per-formance. Although the model has been developed and validated for the prediction of BMR performanceof the specific lactamide-lactic acid system, it nevertheless has broad applicability for and relevance tobroad-based prediction of the performance of immobilised enzyme BMR processes in general, irrespectiveof the specific enzyme or substrate moieties.