We present for the first time experimental evidence that the quantitative accuracy of bioluminescence tomography (BLT) can be significantly improved by incorporating prior spatial distribution of optical properties of heterogeneous media obtained from diffuse optical tomography (DOT). A series of experiments were conducted using a CCD-based scanning system where millimeter-size bioluminescent targets were embedded in a 3 x 3 x 5 cm optically heterogeneous scattering medium. The results show that the BLT images with the recovered optical property distribution in place are considerably better reconstructed compared to that without such prior information, in terms of the location, size and source strength of the targets.