Topochemistry of the initial stages of dissolution of monoclinic single crystals of acetaminophen was studied. Etching pits were identified with the sites of emerging dislocations. Etching of different faces with a solution of ethyl acetate in carbon tetrachloride gave different shapes of etching pits. An interpretation of this result was suggested, based on the analysis of the anisotropy of the crystal structure. Etching of the same crystal face with different etching agents was shown to result in different shapes of etching pits.