Sludge from five full-scale flat-sheet submerged membrane bioreactors has been analysed with reference to the key biochemical fouling characteristics of soluble microbial product (SMP) and extracted extracellular polymeric substanccs (EPS). Correlations have been produced between these parameters, and others pertaining to them and membrane permeability. Correlations have also been produced for some of the sludge physical parameters. Results showed the mixed liquor suspended solids (MLSS) to be exponentially correlated to viscosity and filterability to decrease with sludge particle size, as expected intuitively and from previously reported correlations. In common with many other reported studies, the sludge filterability and membrane permeability were both found to loosely correlate with the carbohydrate fraction of the SMP.