Summary The authors studied the combination of Kathon(R) CG and Germall(R) II (0.1%-0.1%) in hydrophilic creams. Their objective was to find an alternative to the use of parabens. Kathon(R) CG was chosen due to its antimicrobial effectiveness and its broad spectrum of activity. It must be indicated, however, that it has only a weak action against Staphylococcus aureus. In order to reinforce its microbicidal action it was combined with Germall(R) II. The Kathon(R) CG-Germall(R) II combination showed addition, indeed even synergy, with respect to Escherichia coli (Gram negative rod) and Aspergillus niger (fungus). In the case of Candida albicans (yeast) the antifungal effect of Kathon(R) CG dominates. Finally, the combination can have effects from addition to antagonism in the case of the three strains of Staphylococcus aureus tested (Gram positive coccus). The time required to eliminate 10(6) UFC of these bacteria per g of cream can often exceed 48 h. If the concentration of Germall(R) II is increased to 0.3% then the effectiveness of the mixture is markedly reinforced. Caution must be observed, however, due to recent apprehensions expressed by certain dermatologists concerning possible allergic reactions due to Kathon(R) CG. A multi-centre patch test study is currently being carried out with this preservative in the dermatological clinics of the five Swiss university hospitals.