1. A selective late dye concentration dependent on the time is described for 3 triphenylmethane dyes namely bromphenol blue, bromcresol green and iodophenol blue after intravenous application in high dosage in malignant inoculated tumors and experimental tumor metastases in the mouse. 2. The possible mechanisms of this dye concentration phenomenon in the tumor tissue as well as some chances of the eventual therapeutic and tumor diagnostic utilization were discussed.