In the world of cells, the osteoclasts have such a forceful personahty, their destructive potential appears so evident, that the sometimes attempted demonstration of bone resorption occurring in the absence of these cells has not been easily accepted. BAUD (1962), who has produced the first convincing electron micrographs of smooth and rough-bordered lacunae and who has thus understood the resorptive function of the osteocytes, wrote at the same time about their" aspect ost6oclastique". The word" osteolysis" which probably belongs to LERICHE and POLICARD (1928) and which has been used by so many people for so many aspects of resorption, was proposed by B]~ LANGER et al.,(1963) to describe the specific osteocyte-directed bone removal. Of late, the role of the cell has further been emphasized by referring to the phenomenon after HANS KIND (1951) as" osteocytic osteolysis"(B~ LANGER et al., 1967; B~ LANGER et al., 1968). A complete review of the literature on this subject is beyond the scope of the present editorial. The author has attempted only to revisit the general background of the concept, reappraise some of the contributions, emphasize the role of instrumentation, point out some obvious unsolved problems and above all, try and guide the current observers in the interpretation of the morphological aspects of pathological material.