The operation of spiral wound modules in industrial plants is affected by many parameters, including the operating conditions, the arrangements of the spiral Wound modules in arrays and the design of the spiral wound module itself. This paper reviews techniques and approaches for the analysis and optimisation of the performance of spiral wound modules. The analysis of the design of spiral wound modules and arrays with a combination of experimental and numerical techniques can help to identify the optimal array arrangements, module geometry and spacer design for specific applications. The onset of fouling as characterised by the decisive point of the onset of fouling known as the critical flux is discussed in the context of minimisation of fouling within modules and arrays. (C) 2004 Elsevier B.V. All rights reserved.