We have developed a random walk model that uses time-dependent contrast functions to quantify the crosssection and the diffusion and absorption coefficients of an optically abnormal target from time-of-flight (TOF) data obtained in time-resolved transillumination experiments1. To substantiate our methodology we have used two different sets of data. The first set of data, provided by colleagues at University College London, are TOF measurements obtained using a solid phantom whose thickness (55mm), optical properties (absorption, ?a=0.006mm-1, transport corrected scattering, ?sc'=0.7mm-1), and characteristics of its abnormal target (size=5mm, optical properties twice those of the background) are close to those of a human breast. The second set of data, provided by colleagues at Politecnico di Milan, are TOF measurements on a 50mm thick phantom (?a=0.01mm-1, ?sc'= 1mm-1) in which two 10mm abnormal targets (one abnormally scattering, ?sc'=2mm-1; one abnormally absorbing and scattering, ?a =0.04mm-1, ?sc'=2mm-1), are embedded. None of these data includes very short path photons whose measurements are clinically impractical. Using our time-dependent contrast functions, we were able to estimate the size and optical properties of the targets with an error margin of 3-25%.