Two hundred and forty-seven strains of micro-organisms were isolated from the urinary tract of 121 patients with neurological complaints leading to paraplegia. The commonest infecting organism was E. coli and the commonest type of Proteus was P. mirabilis. Infections with more than one type of organism were present in 37% of urine specimens, and in such cases the incidence of E. coli was lower and that of Strep. faecalis higher than the incidences in infections with only one type of organism. No evidence was found which might suggest that the various bacterial species encountered showed either an undue degree of synergism or of mutual antagonism. Coliforms were the commonest primary pathogens, but Strep. faecalis and Proteus species occurred with the same frequency as the coliforms when they were considered as secondary invaders. The variance between the incidences of various species as reported by different workers is considered to be due to the different illnesses and conditions which predispose to urinary tract infection. It appears that infections in the urinary tract by more than one type of organism at a time occur more frequently in those patients with the more chronic predisposing causes. (Some disparity in findings may also result from the differing taxonomic methods employed by different workers, but this is probably insufficiently important to account for the largest differences.