The effects of organic acidic drugs on the absorption, excretion and diuretic action of furosemide were studied. Cefalexin, p-aminohippuric acid (PAH), ibuprofen and p-amino salicylic acid (PAS) were selected as organic acidic drugs. The in situ absorption rate and absorption rate constant of furosemide (30$mu{M}$) were significantly (p<0.05) decreased by 30$mu{M}$ of cefalexin, PAH, ibuprofen and PAS in rat small intestine. The plasma concentration of furosemide was significantly (p<0.01) increased by cefalexin, PAH and ibuprofen in rabbits. But the urinary excretion rate, renal clearance and diuretic action of furosemide were significantly (p<0.05) decreased by cefalexin, PAH, ibuprofen and PAS in rabbits.