The relation between chemical etch pits and dislocations has been studied in thin single‐crystal foils of copper. Both deformed and as‐grown crystals in {111} orientations were employed. A procedure was developed for etching thin foils so that both the etch pits and dislocations were simultaneously revealed by transmission electron microscopy methods. Results are also presented from companion studies of unetched foils and replica studies of etched surfaces. Although a relation was found between etch pits and dislocation emergent points, a one‐to‐one correspondence did not exist. A discussion is presented of other defects which may nucleate etch pits, including some experimental results on deformation‐produced prismatic dislocation loops. The relation of the present results to dislocation studies by etching methods alone is discussed.