OBJECTIVES:  To explore the adherence of Aminoglycoside (Gentamicin,Tobramycin, Amikacin) with basic pharmacokinetics and therapeutic monitoring guidelines in Saudi Arabia METHODS:  It is a prospective cross-sectional of Aminoglycoside (Gentamicin, Tobramycin, Amikacin) basic pharmacokinetics and therapeutic monitoring guidelines adherence. It conducted over a 3-Month at King Saud Medical City (KSMC) surgical wards. The guidelines based on basic pharmacokinetics and therapeutic monitoring guidelines. Any patient received Gentamicin followed up by trained pharmacist and supervised clinical pharmacist. The pharmacist measures the adherence of the following elements including; the USA FDA (Food and Drug Administration) labeled indication, all details such as weight, height, bugs culture sensitivity. Moreover, any adjustments of dosage, trough and peak levels and duration of administration recorded on a therapeutic drug monitoring (TDM) form on a systematic basis. All data gathered were statistically evaluated using SPSS version 22. RESULTS:  The total number of patients were 162, which 126 (77.7%) were male and 36 (22.2%) were female and a mean age of 34.34 ± 15.71 (M±SD) years. Of those 22 (13.8%) patients located from general surgery wards and 138 (86.3%) was from orthopedic wards. All patients received Gentamicin only. Ninety-Five (58.6%) non-adherence to FDA labeled indications while 67 (41.4%) adherence to FDA labeled indication. All patients 162 (100%) were non-compliance of Gentamicin duration of infusion administration time. The trough levels of Gentamicin were sub-therapeutic level in 22(13.6%) patients, 3(1.6%) patients' toxic levels, and 115 (71 %) patients have not checked the drug levels. While the peak levels were sub-therapeutic level in 40 (24.7%) patients, 1(0.6%) patients toxic levels, and 119 (73.5%) patients have not checked the drug levels CONCLUSIONS:  There was a poor adherence to Gentamicin basic pharmacokinetics and therapeutics monitoring guidelines. For aiming compliance, and the guidance leads to decrease Gentamicin resistance, prevent the Gentamicin-related problem, improve Gentamicin therapeutic outcome, and avoid the unnecessary additional cost.