The medical literature is replete with dosing guidelines for patients with renal dysfunction. Altering dosing regimens in such patients is particularly important with drugs with a narrow therapeutic index, such as digoxin and the aminoglycoside antibiotics. A variety of methods have been used to devise dosing nomograms.This article reviews the salient features of different methods, and addresses the issues of predictability or unpredictability in attaining desired plasma concentrations of drug. It is suggested that therapy must be individualised, and that the clinician can best plan his therapy by understanding the principles on which dose adjustment is based, rather than using the same nomogram or guideline for each and every patient.