Permeability is an important parameter in the simulation of resin transfer moulding (RTM) process. This is particularly so in the case of 3D braided preform reinforced composites, which have no distinct layers and consequently generally have higher levels of structural integrity than traditional laminated composites. Such braided preforms have the potential for widespread application in aerospace, marine, civil construction structures. The economical and reliable route to manufacture these structures is likely to be using RTM techniques. This paper, therefore, examines the processing issues connected with 3D braided preform using radial permeability measurements.