All U.S. and most European citizens, even infants, need a valid passport to enter Turkey for stays of up to 90 days. U.S. citizens also need to purchase a visa, which can be done at the official point of entry for $20 USD (as of 01 April 2004), UK citizens purchase visa for 10 GBP, most European nationals purchase visa for 10 Euro.
Canadian citizens need only a valid passport to enter Turkey for stays of up to 90 days. Children under 16 may be included on a parent’s passport but must have their own to travel alone.
Citizens of the United Kingdom need a valid passport to enter Turkey for stays of up to 90 days. Children under 16 may travel on an accompanying parent’s passport. U.K. citizens also need to purchase a visa, which can be done at the point of entry for £10.
An important amendment to the Entry Requirements to Turkey for foreign passport holders – a blank page in passport required for visa stamp. Until December 31st this will be flexible and if a foreign passport does not have a blank page you will be issued a one-off “Entry-Exit form” with your entry-exit stamp on there. You should carry this form with you in Turkey and present it to the border officers, when you leave Turkey. However after the 31st of December the entry will be refused if a passport does not have a blank page for a visa.
Information Source : The Ministry of Foreign Affairs of Turkey