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Since influenza vaccines are propagated in embryonated chicken eggs, they contain residual egg proteins (mostly ovalbumin). This could lead to the induction of allergic reactions in vaccinated individuals that are allergic to egg. The ovalbumin content in six influenza vaccines, available on the Swedish market in the autumn of 2004, was studied using a commercial ELISA kit. The results show a high degree of variation in ovalbumin content between the different influenza vaccines, ranging between 28 ng/ml and 1.1 microg/ml. No vaccine, however, had an ovalbumin concentration above the limit of 1.0 microg per dose (i.e. 2.0 microg/ml) set by the European Pharmacopoeia for the actual types of influenza vaccines. Thus results presented here clearly show that a tightening of the limit is fully possible.