Quantification of nonspecific, biological interactions can provide insight on the mechanisms of cellular adhesion and lead to more effective use of liposomes for drug delivery. The nonspecific interactions between both cells and liposomes and a glass plate were measured using total internal reflection microscopy (TIRM), The sphere-plate geometry and high resolution make TIRM well suited for measuring weak, biological forces, The measured potential energies of interaction agree well with theory. Debye lengths calculated independently from solution conductivity measurements agree with the values obtained experimentally with TIRM. These results are the first reported TIRM measurements with cells and liposomes.