ABSTRACT –The properties of different tetracyclines, alizarin red S, calcein, Procion H‐8B® and hematoporphyrin as fluorescent bone and dentin markers have been tested on growing Wistar rats after intraperitoneal injections. Tetracycline, alizarin red S, calcein and Procion H‐8B were individually identifiable by means of appropriate filter combinations of the microscope. This approach may be useful in prolonged studies of bone growth and reactions. If a fifth marker is needed, mixed injection of tetracycline and Procion H‐8B is recommended. In doses necessary for fluorescence examination, the above recommended substances may be regarded as practically nontoxic. In the dentin, tetracycline and calcein seem to be the best fluorescent markers. Hematoporphyrin is not recommended because of poor labeling properties and general toxicity with weight reduction of the