Capillary zone electrophoretic (CZE) methods are gradually gaining acceptance for quantitative analyses in testing laboratories. However, some procedures are often instrument and operator dependent. Modifications to a published procedure for the routine determination of histamine in fish by CZE in our laboratory were necessary to compensate for a different instrument design and set of operating conditions. The major change was to add an internal standard (imidazole) and to use this to assist in peak identification and quantification. The instrument repeatability data for area calculation and migration time variation (CV for area calculation 2.9%, n = 20; CV for migration time variation 0.2%, n = 20) for a fish containing 100 mg/kg histamine were acceptable when the internal standard parameters were factored into the calculations. The levels of histamine in fish were in good agreement with the fluorimetric method currently used in our laboratory. A limit of reporting of 10 mg/kg was achieved by maximizing the sample size/capillary column internal diameter (i.d.) and optimizing instrumental operating parameters.