The aim of this study was to estimate optical properties (mu(a), mu(s), mu(t), mu(s)', alpha, g) of native and coagulated (at 45 degrees C, 600 degrees C, 80 degrees C) lamb brain tissues in visible and near-infrared spectral range in vitro. Optical properties of cerebellum, brainstem, cortical (grey matter), and sub-cortical regions (white matter) of frontal lobe tissues of lamb brain were estimated during this study. Diffused transmittance (T-d) diffused reflectance (R-d), total reflectance (R-t) and total transmittance (T-t) were measured with single integrating sphere method. Data were processed with software (CAL-g3) developed in Biophotonics Laboratory in the Institute of Biomedical Engineering, Bogazici University. As a result, it was stated that both la, and P, values of tissues increased as temperature increases. Also scattering coefficients decreased with the increasing wavelength for all tissue types due to increase in Mie scattering.