An atomic force microscope (AFM) in conjunction with coated colloid probe and cell probe techniques has been used to measure directly the adhesive force between both the protein bovine serum albumin (BSA) and a yeast cell at two different membranes. These were polymeric ultrafiltration membranes of similar MWCO (4000 Da) but of different materials (ES 404 and XP 117, PCI Membrane Systems, UK). The XP 117 membrane is made from a mixture of polymers chosen with the aim of achieving low fouling. The BSA was adsorbed on a 5 mu m silica colloid probe formed from a tipless V-shaped AFM cantilever, The cell probe was created by immobilising a single yeast cell on such a tipless cantilever. Measurements were made in 10(-2) M NaCl solution, It was found for both protein and cell systems that the adhesive force at the ES 404 membrane was greater than that at the XP 117 membrane. The paper shows that coated colloid probe and cell probe techniques can provide useful means of directly quantifying the adhesion of biological materials to membrane surfaces.