The objective of this study is to determine the safety and efficacy of an extended interval aminoglycoside dosing guideline implemented in our neonatal intensive care unit (NICU). A retrospective review of pharmacokinetic data on 44 patients led to the development of an extended interval aminoglycoside guideline utilizing a 5-mg/kg dose given at an interval based on postconceptional age and risk factors that may alter aminoglycoside clearance. After implementation of the new clinical guideline, a retrospective review of patient records was performed. Thirty-six of 43 peak levels were within the goal range. Trough levels were <1 microg/mL in 41 of 46 patients, with no trough >2 microg/mL. Thirty-three patients had clinical or culture proven sepsis and were successfully treated with the new regimen. No difference between pre- and post-treatment blood urea nitrogen (BUN) and serum creatinine values was observed. Hearing evaluations were performed in 32 patients with one failure. The patient who failed the hearing screen, passed a follow-up hearing test. Three deaths, none attributed to infection or the drug, occurred during the evaluation period. The dosing guidelines developed for our NICU patients are safe and effective, although evaluation of the longterm potential for ototoxicity should be performed.