A Pseudomonas aeruginosa biofilm is studied with pulsed field gradient echo NMR. Although not all spectral components are assigned yet, the exptl. results show that a biofilm consists of components with very different diffusion coeffs. The various biofilm components that give motionally narrowed 1H NMR signals, can be grouped into five classes with diffusion coeffs., ranging from 2 * 10-9 to 1 * 10-13 m2 s-1. Investigation of the diffusion behavior of water in the biofilm shows three fractions with different diffusion coeffs. Besides the highly mobile bulk water at least two other fractions with much lower diffusion coeffs. are detected. It is shown that one of the fractions with the low diffusion coeff. probably arises from intracellular water. Also for another component of the biofilm, glycerol, three fractions with diffusion coeffs. that differ more than a factor ten are detected. Also a group of signals exists which result from practically immobile components.