Preterm birth is associated with several complications and serious infections including sepsis which has been reported among the most important causes of infant death in Saudi Arabia. Gentamicin is an essential drug for proven and suspected sepsis.The main Objective Of this work was done to optimize the use of gentamicin in neonates during the first week of life.And to identify the mosr factors infleuence in pharmacokinetic parametres in this diffeculte group of age.