Maitreet al.recently evaluated the accuracy of a set of previously determined population pharmacokinetic parameters for the opioid alfentanil using data from an earlier study in which the drug had been administered using a computer-controlled infusion pump (CCIP). The present study evaluated the accuracy of these same parameters in a CCIP prospectively in two groups of clinically dissimilar patients: 29 healthy female day surgery patients and 11 relatively older and less healthy male inpatients. In addition, another set of pharmacokinetic parameters, previously determined by Scottet al.in the CCIP in 11 male inpatients was also evaluated. The bias and inaccuracy were assessed by the median performance error (MDPE) and the median absolute performance error (MDAPE) in which the performance error was determined as the difference between measured and target serum concentration as a fraction of the target serum concentration. Unlike Maitreet al., the current study found a consistent bias in both populations. The MDPE was +53% and the MDAPE was 53%, with no difference between patient groups. In the 11 patients studied using the Scottet al.pharmacokinetic parameters, the MDPE was +1% and the MDAPE was 17%. The parameters of Scottet al.were further tested by simulating the serum concentrations that would have been achieved had they been used in the CCIP in the first 40 patients; results indicated MDPE of +2% and an MDAPE of 18%. Therefore, reasonably reliable and accurate target serum concentrations of alfentanil can be achieved using the pharmacokinetic parameters of Scottet al.in a CCIP. Furthermore, these pharmacokinetic parameters are more suitable for use in a CCIP than are the population pharmacokinetic parameters of Maitreet al.