Résumé : Treatment of organized mouse nervous tissue cultures with two aminopiperazine compounds produced the formation of cytoplasmic multilamellated bodies; some concentric osmiophilic layers showed, in the electron microscope, a periodicity suggestive of a phospholipid composition. Similar lesions were found in a hamster cell line treated with aminopiperazine, but this drug had a more pronounced effect on a hamster line transformed by adenovirus type 12, with bigger lipid inclusions and a high proportion of necrotic cells. In these transformed cells, drug treatment increased the lipid content by a factor of 7.6 while the increase was only twofold in drug-treated non-transformed cells. The aminopiperazines studied here have antiviral activity but they are too toxic to justify trials in this field; their greater toxicity for tumour cells is, however, of interest. © 1973.