The major objective of this theoretical modeling was to examine the quantitative relationships between the microscopic properties of tissue and the macroscopic in vivo autofluorescence measurements. The modeling was carried out using skin tissue as an example. Monte Carlo simulation was used to model the excitation laser light distribution in and the autofluorescence escape process from skin tissue. The processes of fluorescence escape was modeled as the escape process from an isotropic point source embedded inside the tissue. The fractional contributions of different skin layers to the measured total in vivo autofluorescence signal were calculated and demonstrate good agreements with the results estimated from our laser induced autofluorescence decay experiments. This modeling also yielded the spatial resolution resolvable using tissue autofluorescence imaging. It was found to be worse than diffraction effect limited spatial resolution (equals the wavelength of light) and became significantly degraded for fluorescence sources deep inside the tissue.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.