[en] Oil-in-water emulsions varying in surfactant concentration and manufacturing process were prepared. About 10 experiments were performed to characterize them. The goal of this research was to find Out which tests should systematically be carried Out to assess efficiently the stability and the properties of ail emulsified preparation. Thus, formulation design requires at least the measurement of the droplet size, the determination of the zeta potential, a TurbiScan(R) analysis, the investigation of the stability under centrifugation and freeze/thaw cycles. If the emulsion contains an active substance, stability under storage at 4 degreesC and microscopic analysis are relevant. Quality Control Should be improved by measurements of viscosity and pH. (C) 2003 Elsevier B.V. All rights reserved.