New results are presented on the pharmacokinetics of the fluorescing fraction of Photofrin II in patients with an early cancer in the oesophagus or the buccal cavity. The light-induced fluorescence signal shows a relatively high contrast between tumor and surrounding normal tissue at short times after i.v. injection. The magnitude of this contrast appears to correlate with the staging of the cancer, the more invasive tumors showing the highest contrast. Some early results on the ex vivo fluorescence analysis of biopsies taken on patients injected with the new sensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC) demonstrate the selectivity of this efficient second generation photosensitizer for advanced lung cancer. mTHPC appears to have good properties for photodetection and has a rather high rate of photobleaching. The significant of the latter is discussed in relation to simplifying light application in PDT.