We have developed a remote, optical method for real‐time etch‐rate measurement and extremely precise end‐point detection during reactive‐ion etching of photoresist films. The photoresist solution is doped with a fluorescent dye before spin coating, and the fluorescence from the resulting film is observed to decrease in time as the material is removed by etching. In this manner, we make a rapid, single‐calibration etch‐rate measurement and have determined the etch endpoint with a precision, in film thickness, of ±30 Å.