In the Netherlands, the influenza epidemic of the 2004/'05 season started late. The background value of 3 cases of an influenza-like illness per 10,000 inhabitants per week was exceeded from week 1 until week 14 of 2005. The magnitude of the epidemic was the largest of the last 5 years, namely 104 per 10,000 inhabitants. As usual, the epidemic was caused mainly by influenza-A viruses of subtype H3N2 and to a lesser degree by A/H1N1 and B viruses. The H3N2-virus isolates belonged to the newly emerged variant A/California/7/04, which deviated slightly from the vaccine strain used for the 2004/'05 season. The influenza-B and H1N1 viruses matched the corresponding vaccine viruses well. For the 2005/'06 season, the World Health Organization has recommended the following vaccine composition: A/California/7/04 (H3N2), A/New Caledonia/20/99 (HiNI), and B/Shanghai/361/02.