To optimize phototherapy and photodetection of cancer, one of the important variables is the localization of the dye after injection. To study this in a clinical context, we have constructed an apparatus based on a non-invasive optical fiber that detects the dye by light induced fluorescence. The time course of the fluorescence signal can be used directly for optimizing photodetection. However, complementary information on the detailed localization of the drug by fluorescence microscopy, and a correlation of this data with tumor necrosis efficacy, are necessary to optimize PDT timing. This will be demonstrated for the case of Photofrin II and tetra (meta- hydroxyphenyl) chlorin (mTHPC) and the two sets of data will be compared.