Gentamicin, tobramycin, amikacin, and kanamycin were given subcutaneously in separate trials to healthy adult dogs of both sexes. Daily dosage levels were as follows: gentamicin, 6.6 mg/kg of body weight; tobramycin, 3 mg/kg; amikacin, 15 mg/kg; and kanamycin, 11 mg/kg. Gentamicin, tobramycin, and amikacin were given in divided doses of 8-hour intervals for 5 consecutive 8-hour periods, whereas kanamycin was given in divided doses at 12-hour intervals for 4 consecutive 12-hour periods. Mean 8-hour urine concentrations +/- 1 SD were gentamicin, 107 +/- 33 microgram/ml, tobramycin, 66 +/- 39 microgram/ml; and amikacin, 342 +/- 153 microgram/ml. Mean urine concentrations (+/- 1 SD) for kanamycin were 473 +/- 306 microgram/ml in urine collected between 0 and 6 hours after dosing and 63 +/- 47 microgram/ml in urine collected 6 to 12 hours after dosing.