Data from therapeutic drug monitoring (TDM) services in Department of pharmacy, Yamaguchi University Hospital, for three yaers from January 1987 to December 1989 were reviewed. DMT data were summarized and analized for the relationships between the drug cincentration in serum and its efficacy, adverse effect, or dosage. The drug non-compliance in out- or in-patients was also discussed. Data for aminoglycosides revealed that the dosage adjustment in patients with moderate renal disfunction, whose creatinine dlearances were above 40ml/min, might be unnecessary.