A fractal analysis is presented for the binding of benzopyrene-tetraol (BPT) in solution to anti-BPT attached to diol silica beads in a fiber-optic antibody-based biosensor. The binding rate coefficient, k 1, and the fractal dimension, D f both increase as the BPT concentration in solution increases from 3 × 10 −9to 1.59 × 10 −8M. Predictive relations for k 1 (Sets 1 and 2) and for D f (Set 2 only) as a function of BPT concentration are provided. These relations fit the calculated k 1and D f values in the BPT concentration range reasonably well. Fractal analysis data seem to indicate that an increase in the BPT concentration in solution increases the ‘roughness’ or the state of disorder on the fiber-optic biosensor surface. Fractal analysis data provide novel physical insights into the reactions occurring on the fiber-optic biosensor surface and should assist in the design of fiber-optic biosensors.