Aminoglycosides are still used extensively in the treatment of nosocomial infections with Gram-negative bacteria. However, the treatment is associated with several adverse effects. Aminoglycosides monitoring is therefore essential to prevent toxic accumulations and to reach therapeutic concentrations. A computer program, PHARMONITOR, has been developed to optimize aminoglycosides monitoring, responding to the demands of most clinical daily situations. This program, based on a one-compartment open pharmacokinetics model, is developed for IBM PC-compatible computers, using D-Base III+. It can calculate t1/2, Vd, Cldrug, Cpmax, and the theoretical optimal dose and interval and also evaluates the creatinine clearance. The program has been conceived to allow maximal speed, flexibility, and reliability by the use of (e.g.) a linear least-squares analysis, the possible reference to previous protocols, the extensive use of keywords to classify and recall patients according to their pathologies, the development of messages recommending maximal dose or minimal dosing interval, and increasing the safety of the analysis. We consider the program a valuable tool for adjusting aminoglycoside dosage in individuals.