Objective: Oxygen-dependent quenching of luminescence of metal porphyrin complexes has been used to image the pO(2) distribution over tumor and normal tissue. Methods: An experimental setup is described using a platinum(II)-octaethyl-porphyrin immobilized in a polystyrene matrix as transparent planar sensor. Results: Sensitivity over a broad range is high at low pO(2) values (+/-0.2 mm Hg at 0 mm Hg; +/-1.5 mm Hg at 160 mm Hg pO(2)). Due to intrinsically referencing via lifetime encoding there was no modification of the sensor response in vivo in the dorsal skinfold chamber model with amelanotic melanoma (A-MEL-3) in awake hamsters when compared to the in vitro calibration. pO(2) measurements over normal tissue (25.8 +/- 5.1 mm Hg) and tumor tissue (9.2 +/- 5.1 mm Hg) were in excellent agreement with previous results obtained in this model using a surface multiwire electrode. Conclusions: Using the presented method the surface pO(2) distribution can be mapped with a high temporal resolution of approximately 100 ms and a spatial resolution of at least 25 mu m. Moreover, the transparent sensor allows the simultaneous visualization of the underlying microvasculature.