People of most nationalities need a visa, which can be conveniently obtained at Bahrain International Airport or at the border with Saudi Arabia. A two-week visa on arrival costs BD5 for citizens of Australia, Canada, the EU, New Zealand, USA and 29 other nations. There is a foreign-exchange office next to the immigration counter at the airport and at the border with Saudi Arabia.
Multiple-entry business visas are available for citizens of the above nationalities and are valid for 6 months. They cost BD42. This visa does not entitle you to work.
If you’re transiting through Bahrain and travelling on to Saudi Arabia by land (and can prove it), the visa fee on arrival for all nationalities is BD2.
Visa extensions of up to a month are available in Manama from the General Directorate of Immigration & Passports (17 535 111; Sheikh Hamad Causeway). You must first find a sponsor (a Bahraini friend or your hotel may oblige for a small fee). Extensions cost BD15 for one week and BD25 for more than one week up to one month; they will take up to a week to process. Foreigners overstaying their visas are rigorously fined.