Phosphoinositides play a major role in the interaction between aminoglycosides and renal epithelial cells. We therefore investigated both in vivo and in vitro, in isolated proximal tubules and in various parts of the rabbit kidney, the influence of neomycin, gentamicin and amikacin on the phosphoinositide metabolism. This was carried out by measuring the 32p incorporation into phosphatidylinositol 4,5-bisphosphates (PI-P2) and phosphatidylinositol 4-phosphates (PI-P). In aminoglycoside-treated animals, compared to untreated controls, the 32 p-PI-P2 and 32p-PI-P levels were decreased and increased respectively in proximal tubules and in cortical areas but these levels were unchanged in papilla and in medulla. Similar variations could be obtained after exogenous addition of aminoglycosides. PI-P2 is a key membrane component in the regulation of both the Ca2+ transport and the intracellular Ca2+ mobilization. Thus, the aminoglycoside-induced modifications of the phosphoinositide metabolism may be considered as a primary event in the drug toxicity which may result from alterations in the cell calcium homeostasis.