Aims: Infection of the catheterized urinary tract with Proteus mirabilis causes blockage of the catheter by crystalline bacterial biofilms. The aim of this work is to identify a surface-coating for catheters that is not vulnerable to colonization by Pr. mirabilis. Methods and Results: A parallel-plate flow-cell and phase contrast microscopy were used to follow bacterial adhesion onto polymer films. Experiments with a urease-negative mutant of Pr. mirabilis suspended in buffer or urine, identified agarose as a polymer on which biofilm did not form. In tests with wild-type urease-producing cells in urine, no adhesion of cells onto agarose was observed for 3 h but then as the pH rose above 8.2, the surface rapidly became colonized by crystalline biofilm. Conclusions: In urine at pH below 8.0, Pr. mirabilis does not adhere to agarose-coated surfaces. When the pH rises above 8.2, however, aggregates of crystals and bacteria form in the urine and are deposited on such surfaces. Significance and Impact of the Study: Strategies to prevent the formation of crystalline biofilms on urinary catheters will need to consider both the properties of the surface-coatings and the requirement to prevent the alkaline conditions that induce crystal formation in urine.